Unsaturated alcohols pyrolysis

Flowers et al. have dealt with the thermal gas-phase reactions of methyl-oxirane, other methyl-substituted oxiranes, and ethyloxirane. The kinetics of the processes have been compared. Pyrolysis of these compounds is a first-order, homogeneous, nonradical process the reaction rate is not affected by radical scavengers. A biradical mechanism holds. The thermochemical behavior of cyclopentene oxide and cyclohexene oxide is similar. The primary products are the corresponding carbonyl compounds and unsaturated alcohols. Two mechanistic possibilities have been discussed they are obtained from a common biradical intermediate or the alcohol is formed directly from the oxirane in a concerted manner. Thermolysis of spirooxiranes leads to ketone derivatives via biradicals with homolytic bond cleavage (Eqs. 376, 377). ... 

A procedure for the preparation of allyl alcohol introduced by B. Tollens (1870) and later improved calls for heating glycerol with three successive portions of formic acid to a temperature of 260° (li days) and recovery of the allyl alcohol from the distillate (46% yield). Glycerol monoformate is formed and suffers pyrolysis to the unsaturated alcohol, carbon dioxide, and water. 

The pyrolysis of long-chained saturated alcohols such as 1-docosanol and long-chained unsaturated alcohols such as phytol and solanesol, known to be naturally occurring components of tobacco, was discussed previously. 

Rearrangements and other side-reactions are rare. The ester pyrolysis is therefore of some synthetic value, and is used instead of the dehydration of the corresponding alcohol. The experimental procedure is simple, and yields are generally high. Numerous alkenes have been prepared by this route for the first time. For the preparation of higher alkenes (> Cio), the pyrolysis of the corresponding alcohol in the presence of acetic anhydride may be the preferable method." The pyrolysis of lactones 9 leads to unsaturated carboxylic acids 10 ... 

Sulfeny I chlondes react with allyl alcohols to yield allyl sulfenates, which are in equilibrium with the allyl sulfoxides [12] (equation 9a) These products can be oxidized to the corresponding sulfones (equation 9b) Pyrolysis of the sulfoxides gives sulfines or evidence for the presence of sulfmes Pyrolysis of sulfones leads to unsaturated compounds by extrusion of sulfur dioxide [12] (equation 9c)... 

Thies ° has shown that the 1,3-oxy-Cope rearrangement can be used to advantage as a two-carbon ring expansion method (equation 9). ° Addition of vinyllithium to a cyclic p. -unsaturated ketone (6), followed by pyrolysis of the TMS ether (7) of the resulting alcohol, gives predominandy the 1,3-rearrangement product (8). 

The pyrolysis of allyl vinyl ethers derived by acid- or mercuric ion-catalyzed ether exchange of ethyl vinyl ether or substituted vinyl ethers with allylic alcohols produces the corresponding y, 8-unsaturated aldehydes or ketones, respectively. 

Unsaturated compounds are obtained in good yield and often without isomerization by pyrolysis of esters of the requisite alcohol. These pyrolyses generally proceed with considerable stereoselectivity, yielding mostly the cis-olefin. A review of pyrolytic cw-eliminations has been provided by DePuy and King.23 The experimental technique is very simple the ester is heated as liquid or vapor at 300-500°. Working up of the product is also simple since neither a solvent nor another reactant is present. Pyrolysis of 1,2-dimethyl-propyl acetate at 500° gives pure 3-methyl-1-butene in 72% yield pyrolysis of 1,3-dimethylbutyl acetate also proceeds only in one direction, yielding 4-methyl-l-butene,24 and it is to be noted that in these cases olefin formation does not follow Saytzeff s rule ... 

The structure of the unsaturated C45 polyisoprenoid alcohol, solanesol, was established in 1956 by Rowland et al. (3359). Despite the fact that solanesol was one of the major individnal components of the extractable waxes from tobacco, its pyrolysis was not reported until 1962. While Lam (2255) favored the satnrated hydrocarbons as the major precursors in tobacco of PAHs in smoke, Wynder (4294) considered both the satnrated hydrocarbons and the phytosterols to be the major precnrsors. Wright (4282) proposed that the phytosterols and other terpenoids snch as solanesol were the major precursors in tobacco of PAHs in smoke. In spite of their differences of opinion on the relative importance of these tobacco components in their contribntion to smoke PAHs, they collaborated on several stndies in the late 1950s (4355, 4356). Snbseqnently, the satnrated hydrocarbons, the phytosterols, and other terpenoids snch as solanesol were shown to be important in the formation of PAHs in tobacco smoke (3251, 3269, 3291, 3616). 

Myosin see Muscle proteins Myrcene a triply unsaturated acyclic monoterpene hydrocarbon. M is a pleasant smelling liquid, M, 136.24, b.p.,2 55-56°C, p 0.8013, n 1.470. It is a component of many essential oils, and it is prepared for the perfumery industry by pyrolysis of p-pinene (from oil of turpentine). M. is al used commercially for the preparation of isomeric acyclic monoterpene alcohols and their acetates... 

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