Benzyl chloride, pyrolysis

The pyrolysis temperature and the rate of addition are chosen such that about 50% of the acid chloride is recovered as 2-toluic acid after hydrolysis. Under these conditions only a small amount of benzyl chloride and polymeric material is formed in addition to benzocyclobutenone. The percentage of reactant conversion depends not only on the pyrolysis temperature, but also on the pressure in the reactor and on the rate of reactant addition. It is advisable, therefore, to optimize the pyrolysis temperature in trial runs keeping the other variables constant. 

Thermolysis on insulating wool. Kaowool or other refractory wools are valuable for reduced radiative heat losses from a hot crucible. However, their use causes some increase in the extent of pyrolysis of substrate vapor by the crucible assembly and this, in rare instances, may spoil a metal atom synthesis. Only one example is known at present. The reaction of palladium atoms with benzyl chloride gives very low yields of t73-benzylpalladium chloride when the palladium is evaporated from an alumina crucible insulated with Kaowool, but a 30-50% yield with an uninsulated crucible. It has been established that this is due to enhanced formation of product-destroying radicals on the hot Kaowool. 

Another chlorinated derivative of polystyrene is poly(vinyl benzyl chloride), CAS 121961-20-4, with the formula [-CH2CH(C6H4CH2CI)-]n. This polymer is a mixture of 3-and 4- isomers in 60/40 ratio. The results for a Py-GC/MS analysis of a sample with M = 100,000 are shown in Figure 6.4.2. The pyrolysis was done at 600° C in He at a heating rate of 20° C/msec. with 10 sec. THT. The separation was done similarly to that for other polymers given previously as examples, on a Carbowax column with the GC starting at 40° C with a ramp of 2° C/min. up to 240° C and a final oven time of 20 min. (see Table 4.2.2). 

Figure 6.4.2. Result for a Py-GC/MS analysis ofpoly(vinyl benzyl chloride) M = 100,000 (mixture of 3-and 4- isomers in 60/40 ratio). Pyrolysis done on 0.4 mg material at 60(f C, with the separation on a Carbowax type column.

There have been a number of studies of magnetic fields upon radical recombination using steady-state techniques of photolysis or pyrolysis. They have variously found large or small effects, which are not always consistent with the theoretical predictions [304—306]. However, using laser flash photolysis techniques to provide fast time resolution, Turro et al. [307] followed the combination of benzyl radicals within hexadecyltrimethyl ammonium chloride micelles in water. The combination occurs over times < 100 ns. A magnetic field of 0.04 T reduces the rate of recombination by almost a factor of two. Such a magnetic field... 

Flash vacuum pyrolysis (FVP) of o-substituted benzylidene and benzyl chlorides154 was found to be a convenient method for the preparation of 1-chlorobenzocyclobutene, anthracene or benzofuran. In the case of o-methylbenzylidene chloride at 700 °C, 89% 1-chlorobenzocyclobutene were formed. Several benzylidene chlorides having different o-substituents were also pyrolyzed. Either o-benzylbenzylidene or o-benzylbenzyl chlorides gave anthracene in good yield. These processes were believed to proceed as shown in equation 70. 

Vinyl chlorides The anion can be alkylated by alkyl iodides (HMPT) or benzylic bromides in high yield. On pyrolysis at 160°, the products are converted into vinyl chlorides (cis- and trans-isomers). 

Surface properties of unmodified carbon-silica adsorbents (carbosils X, H, B, Y) and the same adsorbents modified with the products of pyrolysis of n-heptanol (H) and benzyl alcohol (B) in an autoclave (A) and dynamic reactor (R). The carbosils were prepared by the pyrolysis of methylene chloride adsorbents X and Y), n-heptyl alcohol (H) and benzyl alcohol (B) on the silica surface... 

Pyrolysis of pyridine derivatives is a method for allylic and benzylic deamination the preparation of nitriles from aldehydes, and the preparation of isocyanates from acid chlorides or hydrazides Flash vacuum pyrolysis continues to yield interesting reactions and products. Recently, it has been reported that quite sensitive acetylene derivatives can be obtained by this method from 4-alkylideneisoxazol-5(4H)-ones by ring degradation. On the other hand, 2 carbamyl azide molecules cyclize under these conditions to form l,2,4-triazolidine-3,5-dione 1,2-ylids . 2H-Cyclohepta[b]furan-2-ones have been obtained by ring expansion of phenyl propiolates... 

Scheme 212 Synthesis of (-l-)-monomorine I (1562) and (5f,9 )-indolizidine 195B (1564) by Randl and Blechert. Reagents and conditions (a) hept-1-en-3-one, 3-benzyl-5-(2-hydroxyethyl-4-methylthiazolium chloride (5 mol%), NEts, 65 °C, 18 h (b) flash vacuum pyrolysis, 500 °C, 15mbar (c) Hoveyda—Grubbs catalyst (7), CH2CI2, reflux, 4 h (d), H2 (1 atm), 10% Pd/C, MeOH, rt, 48 h, then chromatography.

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