Double bonds in hydrocarbons

Double bonds in hydrocarbons are indicated by changing the suffix -ane to -ene, and triple bonds are indicated by... 

The properties of some boron hydrides along with those of other volatile hydrides are shown in Table 13.2. A very interesting reaction that diborane undergoes is one in which it reacts with double bonds in hydrocarbons. The reaction can be shown as... 

Since it is often troublesome to indirectly introduce conjugated double bonds in hydrocarbon chains starting from polymers containing separated olefinic unsaturations, the possibility of building up macromolecules possessing conjugated diene systems in a sin e step is of interest. 

Double bonds in hydrocarbons are indicated by changing the suffix ane to ene, and triple bonds by changing to yne. The position of the multiple bond within the structure is indicated by the number of the first or lowest-numbered carbon atom attached to the multiple bond. For example ... 

Hydrogenation reactions are used to add hydrogen across double bonds in hydrocarbons and other organic compounds. Use average bond energies to calculate for the hydrogenation reaction. 

Proton chemical shift data from nuclear magnetic resonance has historically not been very informative because the methylene groups in the hydrocarbon chain are not easily differentiated. However, this can be turned to advantage if a polar group is present on the side chain causing the shift of adjacent hydrogens downfteld. High resolution C-nmr has been able to determine position and stereochemistry of double bonds in the fatty acid chain (62). Broad band nmr has also been shown useful for determination of soHd fat content. 

When applying this principle to replacement names generated from fusion nomenclature, it is essential to keep in mind that fusion names for hydrocarbons ending in -cycloalkene are for fully unsaturated skeletons the -ene ending implies whatever number of double bonds may be necessary, without a multiplier. Thus (117) has six double bonds in the twelve-membered ring, and one must add ten hydrogens to saturate it to the stage of a simple benzene derivative, compound (118). 

Like NR, SBR is an unsaturated hydrocarbon polymer. Hence unvulcanised compounds will dissolve in most hydrocarbon solvents and other liquids of similar solubility parameter, whilst vulcanised stocks will swell extensively. Both materials will also undergo many olefinic-type reactions such as oxidation, ozone attack, halogenation, hydrohalogenation and so on, although the activity and detailed reactions differ because of the presence of the adjacent methyl group to the double bond in the natural rubber molecule. Both rubbers may be reinforced by carbon black and neither can be classed as heat-resisting rubbers. 

Although it is possible to conceive of alicyclic hydrocarbons containing more than a triple bond or two double bonds in the carbocyclic ring, such ring structures are usually either unstable or have transient existence. 

This is a linear polyester containing phthalic anhydride to ensure hydrocarbon solubility and maleic anhydride to enable copolymerisation to take place, esterified with 2-propanediol. The ester is dissolved in styrene which initially acts as the solvent and subsequently as film former when it is copolymerised with the double bond in the ester by free radical induced polymerisation. 

Unsaturated hydrocarbons are quite reactive —in contrast to the relatively inert saturated hydrocarbons. This reactivity is associated with the double bond. In the most characteristic reaction, called addition, one of the bonds of the double bond opens and a new atom becomes bonded to each of the carbon atoms. Some of the reagents that will add to the double bond are... 

Butadiene-1,3 and Cyclopentadiene.—The value 1.46 A. for the single bond between conjugated double bonds in butadiene-1,3 and cyclopentadiene has been discussed already in connection with the values found in other hydrocarbons containing conjugated systems.16 Penney s10 predicted value for the conjugated bond in butadiene, 1.43 A., appears to be a little too low. 

Triethyiaiuminum, Al (CH2 CH3)3, has long been used in the chemical indushy in the production of alkenes— hydrocarbons that have CDC double bonds. In the presence of triethyiaiuminum, two or more ethylene molecules... 

Nickel metal successfully catalyzes the hydrogenation of double bonds in unsaturated hydrocarbons such as propylene and butene. Can this metal also catalyze the dehydrogenation of alkanes such as propane and butane ... 

Compared with monocyclic aromatic hydrocarbons and the five-membered azaarenes, the pathways used for the degradation of pyridines are less uniform, and this is consistent with the differences in electronic structure and thereby their chemical reactivity. For pyridines, both hydroxylation and dioxygenation that is typical of aromatic compounds have been observed, although these are often accompanied by reduction of one or more of the double bonds in the pyridine ring. Examples are used to illustrate the metabolic possibilities. 

Another approach was developed by Scott in the 1970 s (7.8) which utilises the same mechanochemistry used previously by Watson to initiate the Kharacsh-type addition of substituted alkyl mercaptans and disulphides to olefinic double bonds in unsaturated polymers. More recently, this approach was used to react a variety of additives (both antioxidants and modifiers) other than sulphur-containing compounds with saturated hydrocarbon polymers in the melt. In this method, mechanochemically formed alkyl radicals during the processing operation are utilised to produce polymer-bound functions which can either improve the additive performance and/or modify polymer properties (Al-Malaika, S., Quinn, N., and Scott, 6 Al-Malaika, S., Ibrahim, A., and Scott, 6., Aston University, Birmingham, unpublished work). This has provided a potential solution to the problem of loss of antioxidants by volatilisation or extraction since such antioxidants can only be removed by breaking chemical bonds. It can also provide substantial improvement to polymer properties, for example, in composites, under aggresive environments. 

The alkene series of hydrocarbons is characterized by having one double bond in the carbon chain. The characteristic formula for members of the series is C H2 . Since there must be at least two carbon atoms present to have a carbon-to-carbon double bond, the first member of this series is ethene, C2H4, also known as ethylene. Propene (propylene), C,Hh, and butene (butylene), C4HK, are the next two members of the series. Note that the systematic names of these compounds denote the number of carbon atoms in the chain with the name derived from that of the alkane having the same number of carbon atoms (Table 21-2). Note also that the characteristic ending -ene is part of the name of each of these compounds. 

Biosynthesis of triene pheromone components with a triene double bond system that is n-3 (3,6,9-) are probably produced from linolenic acid [49]. Moths in the families Geometridae, Arctiidae, and Noctuidae apparently utilize linoleic and linolenic acid as precursors for their pheromones that must be obtained in the diet,since moths can not synthesize these fatty acids [50]. Most of the Type II pheromones are produced by chain elongation and decarboxylation to form hydrocarbons [51]. Oxygen is added to one of the double bonds in the polyunsaturated hydrocarbon to produce an epoxide [49]. 

Most moth sex pheromones that are straight chain hydrocarbons also usually have an odd number of carbons. Most of these are polyunsaturated with double bonds in the 3,6,9- or 6,9-positions, indicating that they are derived from linolenic or linoleic acid, respectively [49,51]. Iinolenic and linoleic acid cannot be biosynthesized by moths so they must be obtained from the diet [75]. A few even chain-length hydrocarbon sex pheromones have been identified that also have 3,6,9- or 6,9-double bond configurations [49], indicating they too are derived from linolenic or linoleic acids however, it is not known how these even chain hydrocarbons are formed. 

The double bonds of allene are said to be cumulated because one carbon (the central carbon) participates in two double bonds, i) Hydrocarbons whose molecules have cumulated double bonds are called cumulenes. 

A hydrocarbon of the ethylene series, containing two double bonds in the molecule. Dipentamethylene Thiuram Tetrasulphide DPTT, accelerator. 

There is a carbon to carbon double bond in this hydrocarbon. This is an alkene. 

Polyunsaturated fatty acids are characterized by a large number of C = C double bonds in their hydrocarbon chain. Stearic acid has no C = C double bonds and therefore is not unsaturated, let alone polyunsaturated. But eleostearic acid has three C = C double bonds and thus is polyunsaturated. Polyunsaturated fatty acids are recommended in dietary programs since saturated fats are linked to a high incidence of heart disease. Of the lipids listed in Table 28-2, safflower oil has the highest percentage of unsaturated fatty acids, predominately linoleic acid, an unsaturated fatty acid with two C=C bonds. 

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