Hydrocarbons, branched ketones

Because branched ketones and aromatic hydrocarbons are used for their cost/performance benefits, they became the solvents of choice for many apphcations. Numerous solvent systems had to be reformulated to comply with Rule 66. This usually meant an increase in cost, sometimes accompanied by performance degradation. Rule 66-type regulations were adopted in many other states and cities as well. Federal specifications for coatings and many other solvent-containing materials also incorporate Rule 66 requirements. 

Aliphatic ketones are oxidised in both acetonitrile [1,2] and trifluoracetic acid [3] at potentials less positive than required for the analogous hydrocarbons. The oxidation process is irreversible in both solvents and cyclic voltammetry peak potentials are around 2.7 V V5. see. Loss of an electron from the carbonyl oxygen lone pair is considered to be the first stage in the reaction. In acetonitrile, two competing processes then ensue. Short chain, a-branched ketones cleave the carbon-carbonyl bond to give the more stable carbocation, which is then quenched by reaction with... 

Oxygenated derivatives of hydrocarbons Methyl-branched ketones... 

Zeolites have been shown to be good adsorbents for H20, NH3, H2S, NO, NOz, S02, and C02, linear and branched hydrocarbons, aromatic hydrocarbons, alcohols, ketones, and other molecules [16,103,104],... 

The study of zeolites as adsorbent materials began in 1938 when Professor Barrer published a series of papers on the adsorptive properties of zeolites [28], In the last 50 years, zeolites, natural and synthetic, have turned out to be one of the most significant materials in modem technology [27-37], Zeolites have been shown to be good adsorbents for H20, NH3, H2S, NO, N02, S02, C02, linear and branched hydrocarbons, aromatic hydrocarbons, alcohols, ketones, and other molecules [2,31,34], Adsorption is not only an industrial application of zeolites but also a powerful means of characterizing these materials [1-11], since the adsorption of a specific molecule gives information about the microporous volume, the mesoporous area and volume, the size of the pores, the energetics of adsorption, and molecular transport. 

The issue of stereoselectivity of alkene formation from acyclic tosyl- or trisyl-hydrazones has been addressed in only a few cases. For straight chain ketones, there is a preference for m-alkene formation (see Scheme 67). A few other examples appear to give lower ratios, which is surprising in view of several reports of highly cis selective reactions in which the vinyllithium intermediate was trapped with electrophiles.Hydrocarbon branching in the a -position degrades the stereoselectivity considerably (Scheme 67). 

Aromatic compounds > conjugated alkenes > alicyclic compounds > organic sulfides > unbranched hydrocarbons > mercaptans > ketones > amines > esters > ethers > carboxylic acids > branched hydrocarbons > alcohols... 

First of all, it should be pointed out that the rate of oxidation in the series of normal paraffin hydrocarbons increases rapidly with the length of the hydrocarbon chain. Note also that branched-chain paraffinic hydrocarbons are oxidized more slowly than normal paraffins with the same number of hydrocarbon atoms. This may seem surprising, since the hydrogen atom is more easily separated from a tertiary carbon atom than from a secondary, let alone a primary carbon atom. In this case, the cleavage of the C—H bond is apparently not the limiting step, with the rate of the process being determined by the stability of intermediate oxidation products. The oxidation of normal paraffinic hydrocarbons produces aldehydes, more reactive compoimds, whereas the oxidation of isoparaffinic hydrocarbons yields ketones, more stable species. This dependence of the relative reactivity of paraffins on their structure is directly related to their motor properties (octane number) and explains why branched paraffins exhibit higher antiknock properties [93]. 

Other commonly occurring chemical groups ia essential oils iaclude aromatics such as P-phenethyl alcohol, eugenol, vanillin, ben2aldehyde, cinnamaldehyde, etc heterocycHcs such as iadole (qv), pyra2iaes, thia2oles, etc hydrocarbons (Liaear, branched, saturated, or unsaturated) oxygenated compounds such as alcohols, acids, aldehydes, ketones, ethers and macrocyclic compounds such as the macrocyclic musks, which can be both saturated and unsaturated. 

As shown in Table 8, the spray paint solvent is predominately a mixture of several linear aliphatic, branched aliphatic, and cycloaliphatic hydrocarbons, and toluene, xylenes, and ethyl benzene. 2-Butanone (also known as methyl ethyl ketone) was also detected. The breakdown of the solvent mixture by class of compound (aromatic, //-alkane, iso-alkane, cyclic alkane, and others) is shown in Table 9. The solvent appears to be consistent with a mixture of a VM P naphtha... 

Acid and base extractions from this material have been shown to form spontaneous structures in solution termed coercevates that could easily form the basis for protypical membranes (more of this in Chapter 9). Hydrocarbons with chain lengths C15-C30 (both straight and branched chains) and of course PAHs, predominantly pyrene and fluoranthrene, polar hydrocarbons such as aromatic ketones, alkyl and aryl ketones, nitrogen and sulphur heterocycles and most intriguingly purine and pyrimidine analogues have all been observed from this rich carbonaceous cocktail of compounds. Why ... 

Stoddard solvent consists (volume basis) of linear and branched alkanes (30 to 50%), cycloalkanes (30 to 40%), and aromatic hydrocarbons (10 to 20%). Alcohols, glycols, and ketones are not included in the composition, as few, if any, of these types of compounds are expected to be present in Stoddard solvent. Possible contaminants may include lead (<1 ppm) and sulfur (3.5 ppm). 

The slow combustion reactions of acetone, methyl ethyl ketone, and diethyl ketone possess most of the features of hydrocarbon oxidation, but their mechanisms are simpler since the confusing effects of olefin formation are unimportant. Specifically, the low temperature combustion of acetone is simpler than that of propane, and the intermediate responsible for degenerate chain branching is methyl hydroperoxide. The Arrhenius parameters for its unimolecular decomposition can be derived by the theory previously developed by Knox. Analytical studies of the slow combustion of methyl ethyl ketone and diethyl ketone show many similarities to that of acetone. The reactions of methyl radicals with oxygen are considered in relation to their thermochemistry. Competition between them provides a simple explanation of the negative temperature coefficient and of cool flames. 

Surface lipids of plants. The thick cuticle (Fig. 1-6) that covers the outer surfaces of green plants consists largely of waxes and other lipids but also contains a complex polymeric matrix of cutin (stems and leaves) or suberin (roots and wound surfaces).135/135a Plant waxes commonly have C10 - C30 chains in both acid and alcohol components. Methyl branches are frequently present. A major function of the waxes is to inhibit evaporation of water and to protect the outer cell layer. In addition, the methyl branched components may inhibit enzymatic breakdown by microbes. Free fatty acids, free alcohols, aldehydes, ketones, 13-dike tones, and alkanes are also present in plant surface waxes. Chain lengths are usually C20 - C35.136 Hydrocarbon formation can occur in other parts of a plant as well as in the cuticle. Thus, normal heptane constitutes up to 98% of the volatile portion of the turpentine of Pin us jeffreyi.81... 

The decomposition of the alkoxy radical by Reaction 8 occurs by a-scission at the C—C bond attached to the largest hydrocarbon group (185, 229). Straight-chain paraffins produce aldehydes, while highly branched paraffins yield ketones (Reaction 11). The knock resistance of naphthenes may be caused by the stability of the naphthene ring to C—C scission (25). 

The major category of compounds identified in the virgin and recycled HDPE is comprised of aliphatic hydrocarbons, such as pentadecane, hexade-cane, 1-hexadenene, branched alkanes, branched alkenes and others all oligomers of HDPE. Certain differences between virgin and recycled plastics are, however, obvious, e.g. carboxylic acids such as hexadecanoic and oc-tadecanoic acid were found only in the recycled HDPE. Only two ketones were identified, 6-dodecanone and 2-nodadecanone, in the recycled HDPE the former was also present in the virgin material. 

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