Alcohols isomers

Plasticizer molecules can undergo thermal degradation at high temperatures. Esters based on the more branched alcohol isomers are more susceptible to such degradation. This can, however, be offset by the incorporation of an antioxidant, and plasticizer esters for cable appHcations frequently contain a small amount of an antioxidant such as bisphenol A. 

AH eight amyl alcohol isomers are available from fine chemical supply firms in the United States. Five of them, 1-pentanol, 2-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and 2-methyl-2-butanol (/ fZ-amyl alcohols) are available in bulk in the United States in Europe all but neopentyl alcohol are produced (148,149). 

Run frequenqf calculations on the two vinyl alcohol isomers we considered in the last chapter. Optimize the structures at the RHF level, using the 6-31G(d) basis set, and perform a frequency calculation on each optimized structure. Are both of the forms minima What effect does the change in structure (i.e., the position of hydrogen in the hydroxyl group) have on the frequencies ... 

Reduction of the ketone carbonyl of cis-1, 2,3,4,4a,9b-hexahydro-8-hydroxydi-benzofuran-3-one with trifluoroacetic acid and triethylsilane at 0° produces a mixture of the a- and /3-isomers of the C3 alcohol with an u / ratio of 1 4 (Eq. 211).394 This result can be compared with the isomer ratio of 100 1 that results when sodium borohydride is used as the reducing agent.394 The same cis pair of alcohol isomers is formed in 77% combined yield, but in a reversed ratio of a /3 = 4 1, when the less saturated tetrahydrodibenzofuran analog is used as the substrate (Eq. 212).394... 

Torsion around C—C and C O bonds connects different alcohol isomers. The analysis of interactions between torsional states which are concentrated in different torsional wells can provide important information on energy differences between conformations [101, 102]. Conformational isomerism in alcohols is so subtle that it cannot be easily separated from intermolecular influences in... 

The enantiomeric purity was checked by the H-NMR method of Mislow and Raban (60). The absolute configurations of the major alcohol isomers were all R. 

Many transition-metal complexes have been reported as catalysts of this reaction, including [lr(g-Cl)(coe)2]2 [74] and [lrH2(solv.)(PPh3)][SbF6] [75]. The latter catalyst appeared to be a very active and highly selective. The hydroxyl group can be selectively silylated, even in the presence of other potentially reactive C=C and C=0 groups. The order of relative reactivities of alcohol isomers is secondary alcohol > primary alcohol > tertiary alcohol. 

There are basically two approaches to the synthesis of enantiomerically pure alcohols (i) kinetic resolution of the racemic alcohol using a hydrolase (lipase, esterase or protease) or (ii) reduction mediated by a ketoreductase (KRED). Both of these processes can be performed as a cascade process. The first approach can be performed as a dynamic kinetic resolution (DKR) by conducting an enzymatic transesterification in the presence of a redox metal [e.g. a Ru(ll) complex] to catalyze in situ racemization of the unreacted alcohol isomer [11] (Scheme 6.1). We shall not discuss this type of process in any detail here since it forms the subject of Chapter 1. 

Esters and acids from simple carbonylation reactions Alcohols, ethers and esters with higher homologous alkyl groups. Hydrocarbons from hydrogenolysis of the alcohol and its homologs. Ethers from dehydration of the substrate. Esters of the reagent alcohol. s)oiefins from dehydration of the alcohols. Isomeric alcohols. Isomer products (linear/branched 50/50 - 60/40). Only 2-methyl butanol Dimers and trimers of i-butene. 

If the hydrolysis was taken to 50% completion, the theoretical yield of each alcohol isomer was 36.96 g. 

Rate of complex formation between chiral alcohols and DBTA monohydrate in hexane suspension is quite slow (see Figure 1) and numerous separation steps are necessarry for isolation of the alcohol isomers (filtration of the diastereoisomeric complex then concentration of the solution, decomposition of the complex, separation of the resolving agent and the enantiomer, distillation of the product). To avoid these problems, alternative methods have been developed for complex forming resolution of secondary alcohols. In a very first example of solid phase one pot resolution [40] the number of separation steps was decreased radically. Another novel method [41] let us to increase the rate of complex forming reaction in melt. Finally, first examples of the application of supercritical fluids for enantiomer separation from a mixture of diastereoisomeric complexes and free enantiomers [42, 43] are discussed in this subchapter. 

The food additive carnitine (25) is worthy of mention because it has a very close structural relationship to some beta blockers. It is also called vitamin BT. There are many potential routes to this compound, including an asymmetric hydrogenation method.234 236 The method is closely related to that used for Lipitor (Section 31.2.1). Reduction of 4-chloro-3-oxobutyrate provides the desired alcohol isomer. Ester hydrolysis and reaction with triethylamine affords 25. There are two other major approaches one relies on an asymmetric microbial oxidation (Scheme 31.22).237... 

The reduction of citral with alkanols and cycloalkanols to the Z- and /i-alcohol isomers nerol and geraniol using MgO and CaO as catalysts has also been reported.[86] When the reactions were performed by refluxing the mixture with an alcohol/citral molar ratio of 20, excellent yields to the corresponding alcohol... 

Isomers are molecules with the same kinds and numbers of atoms joined up in different ways n-propanol, n-PrOH, and isopropanol, i-PrOH, are isomeric alcohols. Isomers need not have the same functional groups—these compounds are all isomers of C4H8O. 

The occurrence of different isomers in the alcohol series is due to the OH group being located at different positions on the carbon chain. There are no alcohol isomers of the first two members of the series. In C3H7OH there are two possible positions of the OH, e.g. CH3 CH2 CH2 OH and CH3 CH(OH) CH3. The alcohols are named using a system that clearly locates the position of the OH (or ol) group on the carbon chain. 

While the use of zeolites as catalysts for C=0 reduction with alcohols as a reductant goes back to the eighties, stereoselective versions of this reaction have been developed more recently. In this so-called MPV (Meerwein-Ponndorf-Verley) reaction, the reactant carbonyl compound and the reducing alcohol coordinate simultaneously on a Lewis acid centre. In the reduction of 4-t-butylcyclohexanone, the trans product would normally be thermodynamically favored. However, the cis alcohol isomer is economically much more interesting. Van Bekkum and coworkers discovered that in the constrained pores of an Al- or Ti-Beta zeolite, more than 95 % of the product has the cis configuration (59) ... 

Reaction of the two neutral alkylborane adducts with hydrogen peroxide gives two alcohol isomers. In one isomer, the two methyl groups have a cis relationship, and in the other isomer they have a trans relationship. 

The aldehydes arise from the olefin isomers by addition of CO to a carbon atom on either side of the double bond in coupled parallel steps (see Example 5.3 in Section 5.3) and are hydrogenated to the respective alcohol isomers. Fortunately, only the straight-chain aldehyde condenses to a significant extent. In comparison, the detailed network consist of 111 steps. 

Consider as a prototype the network 11.13 of n-heptene hydroformylation, keeping in mind that die arrows represent multistep pathways and that the reactions of higher straight-chain olefins involve still more parallel pathways of internal olefin isomers to aldehyde isomers and on to alcohol isomers. In such networks, all but one of the aldehyde-to-alcohol conversions involve the reaction of an aldehyde group on a secondary carbon atom, so that all these pathways can be assumed to involve essentially the same rate coefficients of their steps. Only the conversion of the straight-chain aldehyde (n-octanal to n-octanol in network 11.13) must be expected to occur with somewhat different rate coefficients. Likewise, all con-... 

C9H10O vinyibenzyl alcohol, isomers, stabilized 30584-69-1 493.31 43.241 2 16729 C9H10O3 alpha-(hydroxymethyl)benezeneacetic acid 529-64-6 520.33 45.841 2... 

Japanese authors have made comprehensive investigations of the rearrangements of oxiranes in the presence of solid acids, bases, and salts.The model compounds employed were cyclohexene oxide and 1-methylcyclohexene oxide. The effects of the acidic and basic properties of the catalysts on the selectivity were interpreted on the basis of the products obtained. The main products are carbonyl compounds and allyl alcohol isomers. Rearrangements of limonene oxide over acids and bases were studied on five different types of Al203 similar research has been carried out on 2- and 3-carene oxides, cis- and trans-carvomenthene oxides and a-pinene oxide. ... 

While activation energies have been published for many isocyanate/ alcohol reactions, relatively few reports have been made of the heat of reaction. Bayer [136] reported a heat of reaction of 52 kcal mole , or 26 kcal equiv", for the hexamethylene diisocyanate/1,4-butanediol reaction. Lovering and Laidler [137] measured heats of reactions for the butyl alcohol isomers with several aromatic isocyanates. Values ranged from 18.5 to 25 kcal equiv . ... 

Propanol does not have a tertiary alcohol isomer. The first of the alcohol series to have these isomers is when = 4, C4H9OH. 

Tertiary alcohols tend to react without rearrangement while secondary alcohols are liable to do so, equations (14) and (15), as discussed in Section 1.9.1.2. Primary alcohols normally fail to react with nitriles even under severe conditions, but this restriction does not apply to benzylic examples (equation 16). In appropriate cases," the Ritter reaction can be stereoselective (Scheme 10). Either alcohol isomer, separately or as a mixture, gave identical mixtures of the two amine products, showing that axial attack on the cation was predominant. 

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