Part I. Chemistry of organic compounds

PART I. CHEMISTRY OF ORGANIC COMPOUNDS

TEXT 1. ORGANIC CHEMISTRY. INTRODUCTION

 

Organic chemistry is concerned with substances containing carbon. The number of known carbon compounds, or organic compounds, exceeds two millions, whereas inorganic substances number 50 thousands. Carbon may thus be singled out from all the chemical elements because of the remarkable diversity of its compounds.

Organic substances play an enormously important role in life. It is these substances that make up plant and animal organisms; they are constituents of our food (bread, meat, butter, and vegetables); they provide materials for the manufacture of clothing (fabrics, leather, etc.), form various types of fuel, and are used by us as drugs, dyes, and so on.

Organic substances have certain distinctive features. They are comparatively readily decomposed by heating, are mostly combustible, and their chemical reactions proceed more slowly as a rule than those of inorganic substances.

There is, however, no sharp dividing line between organic and inorganic substances. The carbon oxides, carbonic acid and its salts ought to be classified as organic substances because they contain carbon, but their properties are such that they are more closely related to inorganic substances.

Apart from carbon, the elements that organic substances contain most frequently are hydrogen, oxygen, and nitrogen; somewhat less frequent constituents are sulphur, phosphorus, the halogens, and certain metals.

Organic substances are easy to identify: when heated, they become charred or else burn with the formation of carbon dioxide.

The term “organic substances” arose early in the XIX^th century, when many scientists believed that these substances were only produced by living organisms through the operation of a “vital force” and could not be produced artificially from inorganic substances. The doctrine concerning a “vital force”, known as vitalism, was unscientific, since it was founded on the belief in some supernatural power. By its contention that organic substances could not be created from inorganic matter, vitalism hampered scientific progress. Nevertheless, it could not, of course, halt the process of the accumulation of knowledge about nature.

In 1828 the German chemist F. Wöhler succeeded in preparing an organic substance (urea) from an inorganic for the first time. In 1854 the French chemist M. Berthelot prepared fats artificially. In 1861 the Russian scientist A.M. Butlerov carried out the first synthesis of a saccharoid substance. Syntheses of substances formerly produced by living organisms only began to follow one another in rapid succession.

Today chemists have not only synthesized many of the organic substances occurring in nature, but have prepared substances that do not occur in nature, such as plastics, various types of rubber, dyes, explosives, and medicines. Chemistry is now on the road to the artificial preparation of proteins, the most complicated substances of all, and beyond doubt this will be accomplished.

Tasks on the text

Memorize the following words and word combinations.

1. substance [`sAbst(q)ns] – вещество 2. carbon [`kRb(q)n] – углерод 3. to be concerned with – изучать, иметь дело с 4. to exceed [Ik`sJd] – превышать 5. to single out – выделять 6. constituent [kqn`stItjuqnt] – компонент, составная часть 7. fabric – ткань 8. leather[`leDq] – кожа 9. drugs – лекарства 10. dyes [daIz] – красители 11. distinctive[dI`stInktIV] – отличительный, характерный

12. combustible[kqm`bAstqb(q)l] – горючий, воспламеняемый 13. carbonic acid[kR`bOnIk `xsId] – угольная кислота 14. halogen[`hxlqGqn] – галоген 15. to char [CR] – обжигать, обугливать(ся) 16. to hamper – препятствовать 17. to halt[hO:lt]– остановить 18. urea[juq`rJq] – мочевина 19. explosives[Ik`splqVsIvz] – взрывчатые вещества 20. saccharoid [`sxkq,rOId] – сахароид, сахаровидный 21. to accomplish[q`kAmplIS] – совершать, выполнять; доводить до конца

Practise the pronunciation of the words given. Make sure you remember their meanings.

Organic [O:`gxnIk], whereas [wFq`rxz], compound [`kOmpaVnd], diversity [daI`vq:sItI], enormously [I`nLmqslI], manufacture [,mxnjq`fxkCq], various [`vFqrIqs], feature [`fJCq], decomposed [,dJkqm`pqVzd], proceed [prq`sJd], however [haV`evq], oxide [`OksaId], frequently [`frIkwqntlI], hydrogen [`haIdrIGqn], oxygen [`OksIGqn], nitrogen [`naItrqGqn], sulphur [`sAlfq], phosphorus [`fOsf(q)rqs], charred [`CRd], dioxide [daI`OksaId], vital [`vaItql], artificially [,RtI`fIS(q)lI], vitalism [`vaIt(q)lIz(q)m], unscientific [,AnsaIqn`tIfIk], nevertheless [,nevqDq`les], accumulation [q,kjHmjq`leIS(q)n], chemist [`kemIst], succeed [sqk`sJd], synthesis [`sInTqsIs], syntheses [`sInTq,sJz], succession [sqk`seS(q)n], synthesize [`sInTqsaIz], chemistry [`kemIstrI], protein [`prqVtJn].

Read, translate and define what parts of speech the words, their derivatives and related words belong to. Consult the dictionary, write out the meanings that are new for you and memorize them.

Chemical – chemically – chemist – chemistry; constitute – constituent; variety – various – variously – vary – varying; comparable – comparative – comparatively – compare – comparison; decompose – decomposed – decomposition; combustible – combustion – combustive; identical – identification – identify – identity; science – scientific – scientifically – scientist – unscientific; accumulate – accumulated – accumulation; succeed – succeedable – succeeder – succeeding – succeedingly.

Read paragraph one and compare organic compounds with inorganic ones in terms of their number.

Read paragraph two and say what it is about.

Find the emphatic sentence, translate it into Russian and comment on it.

7. Read paragraph three and answer the question: “What are distinctive features of organic substances?”

Find the sentence with the word “those”, translate it into Russian and state the meaning of this word.

Read the text up to the end and answer the following questions.

1) Is there a sharp dividing line between organic and inorganic substances?

2) What other elements apart from carbon do organic substances contain?

3) What do you know about vitalism?

4) What scientists succeeded in preparing organic substances?

5) Why is it so important to study organic chemistry?

Translate the following word combinations into English.

Количество известных соединений, играть очень важную роль, удивительное разнообразие, производство одежды, различные виды топлива, как правило, кроме углерода, с образованием двуокиси углерода, жизненная сила, накопление знаний, следовать друг за другом, в быстрой последовательности, вещества, встречающиеся в природе, искусственное создание белков, несомненно, дает нам возможность.

Translate the following sentences into Russian.

1) Органическая химия изучает вещества, содержащие углерод. Их количество превышает 2 млн. 2) Органические вещества сравнительно легко разлагаются при нагревании. 3) Эта доктрина основывалась на вере в некую сверхъестественную силу. 4) Витализм препятствовал научному прогрессу.
5) Немецкому химику Ф. Велеру удалось получить органическое вещество из неорганического. 6) Сегодня химики получили вещества, которые не встречаются в природе.

Tasks on the text

Read, translate and define what parts of speech the words, their derivatives and related words belong to. Consult the dictionary, write out the meanings that are new for you and memorize them.

Acid – acidify – acidize – acidly – acidness –acidulous; effective – effectively – effectiveness; success – successful – succession – unsuccessful; syntheses – synthesis – synthesize –synthetic; toxic – toxicity – toxin – intoxication.

Read the title of the text and say what this text is about judging by its title. Look through the text to find the sentences that support your statement.

Read the text to decide what kind of information – explanatory, clarifying or additional – this text contains as compared to the previous one.

Speak on major trends in Industrial Organic Chemistry.

How do you envisage the future of the organic chemistry?

Tasks on the text

Look through the text and find the word combination “a fractional valence” and explain its meaning.

Discuss the following.

1. What motivated the rapid advance of organic chemistry as science at the beginning of the 19^th century?

2. Can you give the baffling facts scientists faced in the middle of the 19^th century.

3. What is the reason for the diversity of organic compounds?

4. Why do you think it is carbon and not some other element that forms so many compounds?

5. What was the contradiction in the views of A.Butlerov and other scientists?

6. What are the main points of the theory of chemical structure?

Tasks on the text

Find the pairs of synonyms.

Particle, connect, feature, apparently, quadrivalent, account for, explain, evidently, link up, mean/define, exhaust, use up, property, hence, denote, tetravalent, fraction, therefore.

Find the right statement.

1) Structural formulae …

a) show the arrangement of the atoms in space;

b) show the arrangement of the atoms in a molecule;

c) cannot be written in a shortened form.

2) The reason for the diversity of organic compounds is …

a) the destruction of the molecules;

b) the rapid advance of organic chemistry;

c) the ability of the carbon atoms to form chains.

3) Paraffins …

a) mean “little affinity”;

b) are called unsaturated hydrocarbons;

c) do not form the homologues series.

Tasks on the text

Read, translate and define what parts of speech the words, their derivatives and related words belong to. Consult the dictionary, write out the meanings and transcription to the words that are new for you.

Alternate – alternately – alternation – alternating – alternative – alternatively – alternativeness; converse – conversion – convert – converted; dissolvable – dissolvability – dissolve – dissolved – dissolver; mix – mixable – mixture; pure – pureness – purification – purify – purity; separate– separately– separation – separator.

TEXT 6. HYDROCARBONS

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons (arenes), alkanes, alkenes and alkyne-based compounds composed entirely of carbon or hydrogen are referred to as "pure" hydrocarbons, whereas other hydrocarbons with bonded compounds or impurities of sulphur or nitrogen, are referred to as "impure", and remain erroneously referred to as hydrocarbons.

The classifications for hydrocarbons defined by IUPAC nomenclature of organic chemistry are as follows:

1. Saturated hydrocarbons (alkanes) are the most simple of the hydrocarbon species and are composed entirely of single bonds and are saturated with hydrogen; they are the basis of petroleum fuels and are either found as linear or branched species of unlimited number. The general formula for saturated hydrocarbons is C _n H _2n+2 (assuming non-cyclic structures).

2. Unsaturated hydrocarbons have one or more double or triple bonds between carbon atoms. Those with one double bond are called alkenes, with the formula C _n H _2n (assuming non-cyclic structures). Those containing triple bonds are called alkynes, with general formula C _n H _2n-2.

3. Cycloalkanes are hydrocarbons containing one or more carbon rings to which hydrogen atoms are attached. The general formula for a saturated hydrocarbon containing one ring is C _n H _2n

4. Aromatic hydrocarbons, also known as arenes, are hydrocarbons that have at least one aromatic ring.

Tasks on the text

Aliphatic compounds. The aliphatic hydrocarbons are subdivided into three groups (homologous series) according to their state of saturation: paraffins alkanes without any double or triple bonds, olefins alkenes with double bonds, which can be mono-olefins with a single double bond, di-olefins, or di-enes with two, or poly-olefins with more. The third group with a triple bond is named after the name of the shortest member of the homologue series as the acetylenes alkynes. The rest of the group is classed according to the functional groups present.

From another aspect aliphatics can be straight chain or branched chain compounds, and the degree of branching also affects characteristics, like octane number or cetane number in petroleum chemistry.

Aromatic and alicyclic compounds. Cyclic compounds can, again, be saturated or unsaturated. Because of the bonding angle of carbon, the most stable configurations contain six carbon atoms, but while rings with five carbon atoms are also frequent, others are rarer. The cyclic hydrocarbons divide into alicyclics and aromatics (also called arenes).

Of the alicyclic compounds the cycloalkanes do not contain multiple bonds, whilst the cycloalkenes and the cycloalkynes do. Typically this latter type only exists in the form of large rings, called macrocycles. The simplest member of the cycloalkane family is the three-membered cyclopropane.

Aromatic hydrocarbons contain conjugated double bonds. One of the simplest examples of these is benzene, the structure of which was formulated by Kekulé who first proposed the delocalization or resonance principle for explaining its structure. For "conventional" cyclic compounds, aromaticity is conferred by the presence of 4n + 2 delocalized pi electrons, where n is an integer. Particular instability (antiaromaticity) is conferred by the presence of 4n conjugated pi electrons.

The characteristics of the cyclic hydrocarbons are again altered if heteroatoms are present, which can exist as either substituents attached externally to the ring (exocyclic) or as a member of the ring itself (endocyclic). In the case of the latter, the ring is termed a heterocycle. Pyridine and furan are examples of aromatic heterocycles while piperidine and tetrahydrofuran are the corresponding alicyclic heterocycles. The heteroatom of heterocyclic molecules is generally oxygen, sulfur, or nitrogen, with the latter being particularly common in biochemical systems.

Rings can fuse with other rings on an edge to give polycyclic compounds. The purine nucleoside bases are notable polycyclic aromatic heterocycles. Rings can also fuse on a "corner" such that one atom (almost always carbon) has two bonds going to one ring and two to another. Such compounds are termed spiro and are important in a number of natural products.

 

Tasks on the text

One important property of carbon is that it can form certain compounds, the individual molecules of which are capable of attaching themselves to one another, thereby forming a three-dimensional network or a chain. The process is called polymerization and the long molecular chains or networks – polymers, while the source compound is a monomer. Polymers artificially manufactured are referred to as synthetic polymers and naturally occurring as biopolymers.

Synthetic polymers. Traditionally, the industry has produced two main types of synthetic polymer – plastics and rubbers. The distinction is that plastics are, by and large, rigid materials at service temperatures while rubbers are flexible, low modulus materials which exhibit long-range elasticity. Plastics are further subdivided into thermoplastics and thermosetting plastics (thermosets), the latter type being materials where the long chains are linked together by crosslinks, a feature they share with conventional vulcanized rubbers.

However, the distinction in terms of stiffness has become blurred by the development of thermoplastic elastomers (TPEs). Moreover, all polymers, irrespective of their nature, can be reinforced by a very wide range of fillers to produce composite materials.

A polymer is chemically described by its degree of polymerisation, molar mass distribution, tacticity, copolymer distribution, the degree of branching, by its end-groups, crosslinks, crystallinity and thermal properties such as its glass transition temperature and melting temperature. Polymers in solution have special characteristics with respect to solubility, viscosity and gelation.

With a single monomer as a start the product is a homopolymer. Further, secondary component(s) may be added to create a heteropolymer (co-polymer) and the degree of clustering of the different components can also be controlled. Physical characteristics, such as hardness, density, mechanical or tensile strength, abrasion resistance, heat resistance, transparency, colour, etc. will depend on the final composition.

Polymerization. In more straightforward polymerization, alkenes, which are a relatively stable form polymers through relatively simple radical reactions. Conversely, more complex reactions such as those that involve substitution at the carbonyl atom require more complex synthesis due to the way in which reacting molecules polymerize.

As alkenes can be formed in somewhat straightforward reaction mechanisms, they form useful compounds such as polyethylene and polyvinyl chloride (PVC) when undergoing radical reactions, which are produced in high tonnages each year due to their usefulness in manufacturing processes of commercial products, such as piping, insulation and packaging. Polymers such as PVC are generally referred to as " singular " polymers as they consist of repeated long chains or structures of the same monomer unit, whereas polymers that consist of more than one molecule are referred to as " co-polymers ".

Other monomer units, such as formaldehyde hydrates or simple aldehydes, are able to polymerize themselves at quite low temperatures (>-80^oC) to form trimers; molecules consisting of 3 monomer units which can cyclize to form ring cyclic structures, or undergo further reactions to form tetramers, or 4 monomer-unit compounds. Further compounds either being referred to as oligomers in smaller molecules.

Tasks on the text

Answer the questions given.

1) How can you describe the process of polymerization?

2) What is a monomer? What part does it play in the process of polymerization?

3) What is the difference between synthetic polymers and biopolymers?

4) What are the two generic groups of synthetic polymers?

5) Can you describe special characteristics polymers have in solution?

6) Can you name the chemical characteristics of polymers?

7) What is the degree of clustering?

8) What are the physical characteristics of polymers?

9) What polymers and what aliphatic compounds form in the simple polymerization reaction. How can you call such a polymerization reaction in this case?

10) What do complex reactions of polymerization involve and require?

11) What compounds do alkenes form?

12) In what way are polyethylene and polyvinylchloride useful in manufacturing processes?

13) What is the difference between singular polymers and co-polymers.

14) What are trimers? How are they formed?

15) What are tetramers? How are they formed?

Chain-growth. Chain-growth polymerization or addition polymerization involves the linking together of molecules incorporating double or triple chemical bonds. These unsaturated monomers (the identical molecules which make up the polymers) have extra internal bonds which are able to break and link up with other monomers to form the repeating chain. Addition polymerization is involved in the manufacture of polymers such as polyethylene, polypropylene and polyvinyl chloride (PVC).

In the polymerization of ethylene, its pi bond is broken and these two electrons rearrange to create a new propagating center like the one that attacked it. The form this propagating center takes depends on the specific type of addition mechanism. There are several mechanisms through which this can be initiated. The free radical mechanism was one of the first methods to be used. Free radicals are very reactive atoms or molecules which have unpaired electrons. Taking the polymerization of ethylene as an example, the free radical mechanism can be divided into three stages: chain initiation, chain propagation and chain termination.

Free radical addition polymerization of ethylene must take place at high temperatures and pressures, approximately 300°C and 2000 At (atmosphere). While most other free radical polymerizations do not require such extreme temperatures and pressures, they do tend to lack control. One effect of this lack of control is a high degree of branching. Also, as termination occurs randomly, when two chains collide, it is impossible to control the length of individual chains. A newer method of coordination polymerization similar to free radical, but allowing more control involves the Ziegler-Natta catalyst especially with respect to polymer branching.

Other forms of addition polymerization include cationic addition polymerization and anionic addition polymerization. While not used to a large extent in industry yet due to stringent reaction conditions such as lack of water and oxygen, these methods provide ways to polymerize some monomers that cannot be polymerized by free radical methods such as polypropylene.

Step-growth. Step growth polymers are defined as polymers formed by the stepwise reaction between functional groups of monomers. Most step growth polymers are also classified as condensation polymers, but not all step growth polymers (like polyurethanes formed from isocyanate and alcohol bifunctional monomers) release condensates. Step growth polymers increase in molecular weight at a very slow rate at lower conversions and only reach moderately high molecular weights at very high conversion (i.e. >95%).

To solve inconsistencies in these naming methods, adjusted definitions for condensation and addition polymers have been developed. A condensation polymer is defined as a polymer that involves elimination of small molecules during its synthesis, or contains functional groups as part of its backbone chain, or its repeat unit does not contain all the atoms present in the hypothetical monomer to which it can be degraded.

Tasks on the text

Addition polymerization

Addition polymerization, also called polyaddition or chain growth polymerization, is a polymerization technique where unsaturated monomer molecules add on to a growing polymer chain one at a time.

The process takes place in three distinct steps:

1) chain initiation, usually by means of an initiator which starts the chemical process. Typical initiators include any organic compound with a labile group: e.g. azo (-N=N-), disulfide (-S-S-), or peroxide (-O-O-).

2) chain propagation;

3) chain termination, which occurs either by combination or disproportionation. Termination, in radical polymerization, is when the free radicals combine and is the end of the polymerization process.

Addition polymerization unlike condensation polymerization (also known as step-growth polymerization) is specified by the following:

1) high molecular weight polymer is formed at low conversion;

2) no small molecules, such as H₂O, are eliminated in this process;

3) new monomer adds on the growing polymer chain via the reactive active centre which can be: a) a free radical in free radical addition polymerization; b) a carbocation (an ion with a positively-charged carbon atom) in cationic addition polymerisation; c) a carbanion (an anion in which carbon has an unshared pair of electrons and bears a negative charge) in anionic addition polymerization; d) an organometallic complex in coordination polymerization;

4) above a certain ceiling temperature, no polymerization occurs.

Benzol peroxide and aluminium chloride can serve as examples of reaction initiators. Benzoyl peroxide is a radical initiator for the free radical addition polymerization of styrene to produce polystyrene.

Aluminium chloride is an initiator for the cationic addition polymerization of isobutylene to form isobutyl synthetic rubber.

Answer the questions given.

1) What are the three distinct steps of addition polymerization?

2) What compounds serve as typical initiators in the chain-initiation step?

3) What are the specific features of addition polymerization?

4) What are the reactive active centers for each of the three types of addition polymerization?

5) What are carbocation and carbanion?

6) Can you guess on the base of information obtained from the previous text, how organometallic complex can be called in other words?

7) Are there any conditions under which no polymerization occurs?

8) What new information have you obtained from the text as compared to the previous one?

Step-growth polymerization

Step-growth polymerization involves a chemical reaction between multifunctional monomer molecules. In a step-growth reaction, the growing chains may react with each other to form even longer chains. This applies to chains of all lengths. Thus, a monomer or dimer may react in just the same way as a chain hundreds of monomer units long. This is in contrast to a chain-growth polymerization, where only monomers may react with growing chains (In chain-growth polymerization, two growing chains can’t join together the way they can in a step-growth polymerization).

The most common class of step-growth polymerization is called condensation polymerization and the product a condensation polymer, because the chemical reaction by which the monomer molecules bond is often a condensation reaction that produces a small molecule byproduct. A multifunctional monomer is a molecule that has more than one potential reactive site by which it can form intermolecular chemical bonds. The easiest way to visualize a step growth polymerization is a group of people holding hands to form a human chain: each person has two hands (=reactive sites).

A pioneer in step-growth polymerization is Wallace Carothers who invented nylon, a condensation product of hexamethylene diamine and adipic acid. Each monomer has two functional groups (two amino groups or two carboxyl group) and so each monomer can form an amide link with each of its neighbour.

The functionality of a monomer is the number of reactive sites. A functionality of 2 will yield a linear polymer. For instance, hexamethylene diamine and adipic acid create nylon, terephthalic acid and ethylene glycol create PET (Polyethylene terephthalate).

In theory the polymerization will continue to result in a single macromolecule.

The relationship between the extent of the reaction and the average number of monomer units in a polymer chain is given by the Carothers equation. High molecular weight polymer is formed only at high degrees of conversion (extent of reaction). In practice the average length of the polymer chain is limited by such things as the purity of the reactants and the viscosity of the medium.

A monomer with functionality 3 will introduce branching in a polymer and will ultimately form a cross-linked macrostructure. The point at which this three-dimensional structure is formed is known as the gel point because it is signalled by an abrupt change in viscosity. One of the earliest so-called thermosets is known as bakelite.

 

Answer the questions given.

1) What length can chains have in step-growth reaction?

2) What is the difference between chain-growth and step-growth polymerizations?

3) How can you visualize the step-growth polymerization? Can you suggest any other way of showing this type of polymerization?

4) What did you learn about nylon?

5) What kind of relationship does Carothers equation explain?

6) How is the average length of the polymer limited in practice?

7) What is a functionality? Compare monomers with functionality 2 and 3.

8) What is a gel-point?

Tasks on the text

Read part C once again and say how paraffins (naphthenes, olefines and aromatics) are applied in petrochemical industry and what special characteristics of these hydrocarbons specify their applications.

Tasks on the text

Find the pairs of synonyms.

Apply, complex, clean, call for, blend, manufacture, conversion, mix, complicated, production, pure, use, transformation, require.

Find the pairs of antonyms.

Complex, advantage, continuous operation, high, stable, simple, disadvantage, batch operation, unstable, low.

Finish the sentences.

1) The petroleum-chemical industry is of comparatively recent … 2) Professor Silliman mentioned the possibility of using petroleum products for purposes other than … 3) When burning oil, we burn … 4) The product is treated to bring it up to … 5) New processes are developed for quicker or cheaper … 6) The sequence of operations in oil and chemical manufacture is practically … 7) Fine chemicals production call for a high … 8) Batch operation is advantageous in carrying out a …

Translate into English.

Первая скважина в Америке была пробурена в 1959 году. Нефтяные продукты использовались, как правило (as a rule), для освещения и обогрева. Но еще более 100 лет назад великий русский химик И.Д. Менделеев говорил о том, что нефть должна использоваться в качестве химического сырья.

В 1917 г. был разработан процесс получения ацетона из пропилена. Многие нефтяные компании США (Ease, Shell, Standard Oil) начали производство химических продуктов в 1930. Олефины в качестве сырья получали из термического крекинга нефтяных фракций.

После второй мировой войны с реконструкцией нефтепромышленности в западной Европе нефтехимическая промышленность развивалась там быстрее, чем в Восточной.

TEXT 3. SYNTHETIC RUBBERS

 

Natural rubber is obtained from the rubber tree Hevea brasillensis. It is a chain polymer of isoprene (methylbutadiene) in which a certain number of bonds remain and can react with vulcanizing agents such as sulphur, thus giving a rubber more rigid structure due to the cross linking of the hydrocarbon chain.

Synthetic rubbers fall into two general classes according to their uses, the general-purpose rubbers and the speciality rubbers.

The most important general-purpose rubbers have been the SBR rubbers made by copolymerization of butadiene and styrene. In the last years, a new family of synthetic rubbers – stereospecific rubbers – have been developed based on the polymerization of diolefins such as butadiene by catalysts of Ziegler/Natta type. In this reaction chains are built up by linking carbon atom 4 of the molecules with carbon atom 1 of another; the double bonds 1-2 and 3-4 disappear and a new double bond emerges and is available for the formation of cross links. The polymer can then exist in either of two configurations with the linkage of the carbon atoms 1 and 4 either on the same side of the plane of the new double bond (cis-configuration) or on opposite sides (trans-configuration).

Products with a cis-configuration are resilient and elastic, as is natural rubber; products with a trans-configuration are hard and inelastic, as are the natural products guttapercha and balata.

More recently, copolymers of ethylene and propylene, EP rubbers, have been developed. Being completely saturated polymers, they are very resistant to oxidation and the effects of light but do not readily vulcanize. Double bonds can be introduced by copolymerizing ethylene, propylene and hexadiene or cyclopentadiene to produce EPT rubbers (ethylene, propylene, terpolymer). Yet another synthetic rubber of the butadiene/styrene type has been developed in the USA under the trade name Thermolastic. It is transparent, resilient, abrasive resistant, waterproof and does not need vulcanization. Similar rubbers, ABS rubbers, are produced by copolymerization of the three monomers, butadiene, styrene and acrylonitrile.

The speciality rubbers are of various types, of which the best known are butyl rubber, nitrile rubber and chloroprene rubber.

Other speciality rubbers include polysulphide, polyether, polyurethane, acrylic and chlorosulphonated rubbers.

The polymerization reactions involved in the production of synthetic rubbers are carried out in solution or in emulsion. By emulsion polymerization the rubber is obtained as a latex and can be used as such for the manufacture of foamed or dipped goods or can be converted to crumb rubber by coagulation.

Tasks on the text

Find the pairs of synonyms.

Bond, produce, emerge, application, artificial, purpose, obtain, linkage, aim, appear, synthetic, use.

Find the proper definition.

a)Vulcanization; b) SBR rubber; c) isomerization; d) polymerization.

1. The rearrangement of the carbon skeleton of a molecule.

2. Treating rubber with sulphur.

3. The combination of a number of unsaturated molecules of the same or different compounds to form a single large molecule.

4. Synthetic materials made by copolymerization of butadiene and styrene.

5. Say a few words on: a ) Natural rubber. b) The classes of synthetic rubbers. c) The SBR rubbers. d) Stereospecific rubbers. e) Products with a cis-configuration. f) Products with a trans-configuration. g) EP rubbers.

Translate into English.

1) Бутиловый каучук получают полимеризацией изобутилена, нитриловый каучук производится полимеризацией бутадиена и акрилонитрита. 2). Спрос на синтетический каучук продолжает увеличиваться. 3) В будущем синтетический каучук потребуется в еще большем количестве. 4) Строительство нефтехимических комплексов с производством синтетического каучука планируется в некоторых районах нашей страны.

TEXT A

The general-purpose rubbers can be used for most purposes for which natural rubber was formerly the only product available. They are used either alone or in blends with other materials, particularly carbon black, for manufacturing cars and truck tyres, mouldings, extrusions, foot-wear, belting, wire and cable covers, flooring and the whole range of domestic articles. Where necessary they are vulcanized with sulphur or other vulcanizing agents.

The speciality rubbers have mostly been developed to achieve some particular property for specific applications for which general-purpose rubbers would not be technically suitable. They are generally more expensive and are limited in use to the applications for which they are most suited by their individual characteristics, such as resistance to high temperature, resistance to oil and solvents, and high flexural strength.

Butyl rubber is outstandingly impermeable to air and is accordingly widely used for inner tubes and curing bags. It alsohas good electrical properties and is used in wire and cable covers.

Nitric rubbers are extremely resistant to mineral oils, including aromatic oils, and are used for hoses, tubing and gaskets that come into contact with oil products.

Neорrene is resistant to mineral oils other than aromatics, it is also resistant to ozone and is therefore an excellent material for cable covers. Its non-inflammability is important for applications in the building industry.

Ethylene-propylene rubbers, EPR, are outstandingly resistant to ozone and to ageing, and are used for the manufacture of weather strips and window sealings in cars and buildings.

Hypalon rubber is highly resistant to heat and chemicals and, being white, lends itself well to the manufacture of light-coloured articles.

11. Give a title to the text.

12. Read paragraph 1 and answer the question. What are the general-purpose rubbers used for?

13. Read paragraph 2 and answer the question. What properties have the speciality rubbers?

14. Read the rest of the text and answer the questions.

1) What properties has butyl rubber?

2) What is it used for?

3) What properties have nitric rubbers?

4) What are they used for?

5) What is neoprene resistant to?

6) What is it used for?

7) What do you know about ethylene-propylene rubbers?

8) What can you say about hypalon rubber?

15. Say a few words about the uses of synthetic rubbers.

TEXT 4. POLYETHYLENE

Application. A process for the production of high density (0.959-0.968) polyethylene from 99% ethylene using а two-component catalyst system consisting of: (1) a titanium halide and (2) a cocatalyst based on a new class of aluminum hydride compounds:

Description. The catalyst from the preformation tank R₁ is suspended in an aliphatic solvent and then continuously fed to the reactor R₂, where is also sent a continuous flow of monomer. Both temperature and pressure are carefully controlled in order to retain polymer quality.

The polymer slurry, discharged from the reactor, is conveyed to a flash vessel (V₁) where the reaction is stopped and unreacted monomer and inerts are separated, and finally washed in V₂ with an extracting agent, which is recycled from the distillation unit, in order to remove catalyst residues.

The polymer, separated from the solvent and dried, is sent to a conventional blending and extrusion section.

Solvent and extraction agent from the separation and drying units are conveyed to the recovery plant where waxes are removed (V₃); finally in the C₁ column the recycle solvent is obtained as bottom, and the extraction agent as overhead.

Raw Material and Utility Consumption (Per metric ton of pelletized polyethylene):

Ethylene, 100%-Kg	1,090
Solvent, Kg
Low pressure steam, Kg	2.000
Electric power, Kwh
Cooling water, m^3
Fuel, Mkcal

 

Tasks on the text.

POLYISOPRENE

 

Application. A process for polymerizing isoprene in an organic solvent using a two-component catalyst system consisting of: (1) titanium tetrachloride and (2) cocatalyst based on a new class of aluminum hydride compounds:

Description. Fresh and recycled monomers are dried, separated from the polymerization inhibitor and fed to the polymerization line along with the recycle solvent and the catalyst. The polymerization occurs at nearly room temperature and can be performed at a high monomer conversion without gel formation.

After the polymerization line the rubber solution is washed with water to remove the catalyst residues, antioxidant added, and homogenized in a blender. The rubber solution is then sent to the stripping section where a crumb slurry of solvent-free rubber is obtained. The overhead stream consists mainly of solvent and unreacted monomer. The solvent, distilled and dried, is recycled to the polymerization line, while the unreacted monomer is partly recycled and partly sent back to its production line.

The rubber crumbs, separated from water on a vibrating screen and dried, are then sent to baling and wrapping.

 

Raw Material and Utility Consumption (per metric ton of end-product):

Isoprene 100%, Kg	1,030
Polymerization solvent, Kg
Electric Power, Kwh
Steam, Kg	6,600
Cooling water, m^3
Process water, m^3

 

Product Properties:
1,4-Cis, %	≥ 96
Mooney Viscosity, ML (1 + 4) at 100° С	≥ 80
Ash, %	< 0.1
Volatiles, %	< 0.75
Density	~ 0.92
Gel, %	< 1

Fig. 2. Polyisoprene production scheme

TEXT 5. ACETYLENE

 

Application. A process for production of acetylene from naphtha and oxygen.

Description. Oxygen and vaporized naphtha are preheated separately, mixed rapidly and fed through a plurality of parallel channels of a burnerblock to the flame room where the reaction is carried out under partial oxidation conditions. The burnerblock prevents flashback or blowoff of the flame and acts as a distributor and stabilizator together with a system of pilots. In the flame room the main part of the naphtha is burnt, the rest (about 30%) is cracked to acetylene and methane. Practically no olefins or higher acetylenes are produced and therefore the separation of acetylene can be done in a very simple and cheap way. The conversion of naphtha and oxygen is complete. The flame reaches an average temperature of 1400° C. Operating pressure is slightly above atmospheric.

At the end of the flame room the burnergas is cooled rapidly by injection of water. Before the cooled burner-gas can be compressed and separated, soot must be removed in a special water scrubber. The burnergas has the following typical composition (dry basis):

Acetylene	9.3	Vol. %
Hydrogen	42.5
Carbon monoxide	37.3
Carbon dioxide	3.8
Methane	5.5
Higher acetylenes	0.6
Inerts	1.0
	100.0

 

The compressed gas (10 atm) passes to the absorber, where acetylene is removed by N-methylpyrrolidone (NMP), a selective solvent which shows a high acetylene/carbondioxide selectivity. After removing CO₂ from the rich solvent by stripping, acetylene is recovered by desorption and stripping. Finally the higher acetylene and water are removed by stripping under reduced pressure. The acetylene leaving the NMP-wash has a purity of 99.2% and can be further purified in a sulfuric acid wash to about 99.9%. The offgas is suitable for the production of ammonia or methanol.

Yields. Yields of 23 wt. percent are obtained.

 

Tasks on the text.

 

1. Memorize the following words and word combinations.

1. to preheat – предварительно нагревать 2. plurality [pluq`rxlItI] – множество 3. burnerblock – печной блок 4. flame room – жаровая камера 5. flashback – проскок пламени 6. blowoff – продув, срыв пламени 7. to crack - крекировать 8. average temperature [`xvrIG `temprICq] – средняя температура 9. operating pressure [`preSq] – рабочее давление 10. burnergas – печной газ 11. to cool – охлаждать 12. injection – впрыскивание, нагнетание 13. to compress – сжимать

14. soot – сажа, копоть, нагар 15. scrubber [`skrAbq] – скруббер; газоочиститель; колонна для очистки (промывки) газов 16. absorber [qb`zO:bq] – абсорбер, поглотитель 17. selective solvent – избирательный растворитель 18. desorption –десорбция 19. to strip – отпаривать, десорбировать 20. stripping –1) удаление; очистка; снятие верхнего слоя; 2) отгонка легких фракций 21. offgas – отходящий газ 22. yield [ji:ld] – выход

 

2. Read the text and decide if the following statements are true or false.

1) In this process acetylene is produced from naphtha and hydrogen.

2) Oxygen and vaporized naphtha are preheated separately.

3) In the flame room the reaction is carried out under complete oxidation conditions.

4) The burnerblock causes flashback or blowoff.

5) The main part of the naphtha is cracked to acetylene and methane.

6) The average temperature of the flame is 1400 C.

7) Operating pressure is slightly higher than atmospheric.

8) Steam is injected to cool the burnergas.

9) It is necessary to remove soot in a special water scrubber.

10) Desorption and stripping recovers acetylene.

3. Put questions to the words in bold type.

1) Oxygen and vaporized naphtha are fed through a plurality of parallel channels of a burnerblock.

2) In the flame room some part of the naphtha is cracked to acetylene and methane.

3) Practically no olefins or higher acetylenes are produced and therefore the separation of acetylene can be done in a very simple and cheap way.

4) The flame reaches an average temperature of 1400 C.

5) At the end of the flame room the burnergas is cooled rapidly by injection of water.

6) The compressed gas passes to the absorber.

7) After removing carbon dioxide from the rich solvent by stripping, acetylene is recovered by desorption and stripping.

8) The acetylene leaving the NMP-wash has a purity of 99.2%.

9) The off-gas is suitable for the production of ammonia or methanol.

4. Describe the process of acetylene production from naphtha and oxygen.

 

Fig. 3. Acetylene production scheme

TEXT 6. ACETYLENE (II) (BASF)

 

Application. A process for making 99⁺ percent pure acetylene from natural gas and oxygen.

Description. Oxygen and natural gas are preheated in direct-fired heaters to about 1,200°F. The charge gases are mixed in a molar ratio of 0.60: 1.00 oxygen: methane upon being fed to the burner. The burner is a vertical cylindrical unit comprising three sections: mixing chamber, flame room, and quench chamber. The mixing chamber is specially designed to provide rapid yet thorough mixing of oxygen and methane.

The mixed gases are fed to the flame room through a plurality of ports in a burner block designed to prevent backtravel or blowoff. In the flame, methane is cracked according to the endothermic reaction:

2CH₄ → C₂H₂ + 3H₂

 

The combustion of methane supplies sensible and cracking heats. About one-third of the entering methane is cracked; most of the remainder is burned. Over-all conversion of methane is 90-95 percent; conversion of oxygen is complete. The flame reaches an average temperature of 2,700° F. Operating pressure is slightly above atmospheric. Residence time is 0.001-0.01 seconds.

The acetylene is cooled rapidly by a series of sprays located in the lower part of the burner. The cooled gases pass directly to a spray chamber where most of the water is condensed. The gases leave the chamber at 100° F and have the following typical composition (dry basis):

 

Acetylene	8.5%	Methane	4.0%
Hydrogen	57.0%	Higher Acetylenes	0.5%
Carbon monoxide	25.3%	Inerts	1.0%
Carbon dioxide	3.7%	Total	100.0%

 

Before the cracked gas can be compressed and separated, residual soot must be removed. Burner trains have a capacity of 25 tons per day. Polyformers are removed by prescrubbing with selective solvent. The clean cracked gas is then compressed to the head pressure (about 10 atmospheres) of the concentration system.

The cracked gas passes from the compressor to the main absorber, where acetylene is removed by a selective solvent which shows a high acetylene: carbon dioxide selectivity. Carbon dioxide is removed from the rich solvent by a flashing and stripping operation. Acetylene is stripped from the solvent by conventional flashing and fractionation. Higher acetylenes and water are removed by stripping under reduced pressure. The product acetylene has a purity of 99⁺ percent with major impurities being methylacetylene, propadiene and carbon dioxide. 99.9 percent acetylene may be obtained by employing an additional processing step.

Yields. The over-all process yield of acetylene, based on carbon in the natural gas, is 31 percent.

Tasks on the text.

1. Memorize the following terms.

1. direct-fired heater – подогреватель (печь) с огневым подогревом 2. °F, Fahrenheit [`fxr(q)nhaIt] – по Фаренгейту, по шкале Фаренгейта 3. charge[CRG]gas – сырьевой газ 4. burner[`bq:nq] – факел, высокая труба для сжигания отходящих газов 5. mixing chamber [`CeImbq] – смесительная камера 6. quench[kwenC]chamber – охладительная камера 7. port – отверстие 8. backtravel – обратное распространение пламени 9. endothermic [,endqV`Tq:mIk] – эндотермический 10. combustion[kqm`bAsC(q)n] – сгорание 11. remainder [rI`meIndq] – остаток

12. sensible heat – явная (физическая) теплота, теплота нагрева 13. residence time – время пребывания, продолжительность нахождения 14. spray – распылитель 15. inerts[I`nq:ts] – инертные компоненты 16. cracked gas – крекинг-газ 17. burner trains– ряд последовательно соединенных факелов 18. polyformer – полиформер 19. selective – селективный 20. head pressure – напорное давление 21. impurities – механические примеси 22. flashing – мгновенное испарение (парообразование) 23. fractionation [,frxkS(q)`neIS(q)n] – фракционирование, разделение (на фракции); перегонка; ректификация

Tasks on the text

1. Memorize the following terms.

1. triolefin(e)[,traI`qVlIfJn] – углеводород с тремя двойными связями; триолефин 2. disproportionation 1) диспропорционирование (перераспределение атомов или групп между двумя одинаковыми или разными соединениями); 2) самоокисление-самовосстановление 3. disproportionation reaction – реакция перераспределения; реакция превращения одной молекулы в две другие, отличные друг от друга (окисление-восстановление) 4. butene [`bjHtJn] – бутен 5. to upgrade – облагораживать, повышать качество 6. reactor operation – работа реактора 7. diluent [`dIljVqnt] – разжижитель; разбавитель 8. per pass – за один проход, за цикл 9. feed, feed stock – исходное сырье

10. pentene [`pentJn] – пентен 11. to fractionate [`frxkS(q)neIt] – фракционировать, ректифицировать 12. trace quantities [`kwPntqtIz] – очень малые (едва уловимые) количества 13. to deethanize – деэтанизировать, отгонять этан 14. dehydrogenation [,dJhaI`drPGqneIS(q)n] – дегидрирование, дегидрогенизация 15. butadiene [,bjHtq`daIJn] – бутадиен 16. onstream time – период непрерывной работы 17. pounds per square inch gage, psig – избыточное давление, равное 6894,757 Па 18. WHSV, weight hour space velocity – объёмная скорость (количество нефтепродукта на единицу веса катализатора в час)

 

2. Read the text. Complete the following sentences, using information from it.

1) The Triolefin Process converts propylene to…

2) In this process a … reaction is carried out.

3) Propylene is converted approximately by 40 % …

4) It is possible to use … of propane-propylene in the unit feed.

5) Methane, ethane, isobutene and butanes are produced in … quantities.

6) If it is necessary to get a high-purity butane product, it is possible to …the reactor feed.

7) Butene-2 is … for alkylation to produce high octane motor fuel.

8) By reducing acetylene and diolefin content of the feed it is possible to extend …

9) This can be achieved easily by selective …

10) A catalyst containing … can be used for this purpose.

3. Find the English equivalents.

Относительно дешевый, более дорогой, на каждые две моли, циклическая операция, допустимый, рециркулирующий поток, содержание пропана, более тяжелое вещество, подходящий для, предварительно, почти чистый, очистная колонна, дополнительный, относительно недорогой, превосходное сырье для алкилирования, моторное топливо с высоким октановым числом, поставщик, свободный от серы (обессеренный), удовлетворительное ведение процесса.

4. Describe the Triolefin Process.

5. Say a few words about reactor onstream cycle time extension.

TEXT 8. POLYVINYLCHLORIDE

 

Application. A process for the manufacture of PVC resins from vinyl chloride monomer, catalysts and additives.

Description. Two-step batch polymerization process carried out in two reactors in series. During the first step polymerization proceeds in a liquid medium of vinyl chloride monomer; it is a bead formation phase rate in the range 10 to 12%. For this initial phase, a stainless clad, vertical autoclave equipped with very turbulent agitation is used. Operating pressure and agitation conditions set the particle size distribution and the shape of the bead used thereafter as a seed in the second step.

The second step is a growing phase for the seeds; it is performed in stainless clad designed for efficient agitation of a powdery medium. At the end of the polymerization cycle the unreacted monomer is recovered by condensation and directly reused for further polymerization. PVC resin is then discharged from the horizontal autoclave to a classification unit which screens the product to the desired specification. Oversize amounting to 5-10% of total is reduced in size with an appropriate grinder designed not to affect the product properties

Since mass process produces a dry free flowing resin prior to classification the normal capital expenditures associated in suspension PVC process for dewatering and drying are not necessary. The plant is run by a sequential program; the automatic control of operating procedures results in excellent reproducibility of products manufactured.

Tasks on the text.

1. Memorize the following terms.