Hydrogen chloride, addition

Dimethylcyclohexene is an example of an alkene for which the stereochemistry of hydrogen chloride addition is dependent on the solvent and temperature. At —78° C in dichloromethane, 88% of the product is the result of syn addition, whereas at 0° C in ether, 95% of the product results from anti addition.8 Syn addition is particularly common with alkenes having an aryl substituent. Table 4.1 lists several alkenes for which the stereochemistry of addition of hydrogen chloride or hydrogen bromide has been studied. 

TABLE 3. Product distribution in hydrogen chloride addition to halogeno-substituted 1,3-buta-dienes, R1CH=CR2-CR3=CH2... 

SAMPLE SOLUTION (a) The addition of hydrogen bromide in the absence of peroxides exhibits a regioselectivity just like that of hydrogen chloride addition Markovnikov s rule is followed. 

Migration to the double bond (equation 33) is a second type of interaction and is well illustrated by the nature of rearranged products obtained in the hydrogen chloride addition to t-butylacetylene (section II,A,lc) and in the solvolysis of t-butylvinyl derivatives and a-cyclopropylvinyl derivatives (section II,C,2). 

At various temperatures ranging from 200 to 300 °C, fso-propyldichloro-silane was obtained in the highest yield at 220 °C, but decreased as the reaction temperature increased due to the decomposition of iso-propyl chloride. Under these reaction conditions, the yield of fso-propyldichloro-silane was higher compared to those obtained from the direct reaction without hydrogen chloride addition, indicating that the decomposition of iso-propyl chloride was suppressed as expected. The yields generally increased with increased ratios of hydrogen chloride to /so-propyl chloride. 

In the direct reation of cyclopentyl chloride, hydrogen chloride addition to the cyclopentyl chloride reactant did not have much effect but gave about the same result as without hydrogen chloride addition. This may be explained by the rapid decomposition of cyclopentyl chloride to provide enough hydrogen chloride to produce cyclopentyldi-chlorosilane. 

To prepare allylchlorosilanes, the problems of allyl chloride decomposition and diallyldichlorosilane polymerization must be solved.15 The hydrogen chloride addition technique was expected to work for this reaction. 

Dry hydrogen chloride (100 g., 2.75 moles) is passed into a mixture of 100 g. (0.76 mole) of paraldehyde and 100 g. (2.18 moles) of ethyl alcohol cooled in an ice bath. Hood.) The upper layer formed during the hydrogen chloride addition is separated and dried over calcium chloride. Distillation gives 162 g. (69%) of a-chloroethyl ethyl ether boiling at 93-96°. 

A slow flow of anhydrous hydrogen chloride gas is now introduced through the capillary tube E. This hydrogen chloride addition should continue throughout the electrolysis to maintain a saturated solution. A trickle of water is allowed to drip into the porous cup. The rate of water addition determines the voltage requirement of the electrolytic cell. Thus, changes in the rate may be required during the electrolysis, but a convenient initial rate of addition is about 4 1./24 hr. 

In the case of hydrogen chloride addition to a-pinene (5.41), it is likely that the mechanism has a considerable degree of synchronous character for, if the free cation were to be formed, the molecule would rearrange as happens when pinene hydrochloride is allowed to warm up to room temperature. The reason for the instability of pinene hydrochloride... 

It is a surprising fact that a-camphorene is capable of being built up synthetically with comparative ease. In order to accomplish the synthesis, Semmler and K. G. Jonas heated myrcene for four hours in a sealed tube to 250 to 260 by which they obtained a yield of 50 per cent of a fraction with boihng-point 175 to 195 (8 mm.) which afforded a solid hydrogen chloride additive product, melting-point 129 to 130°. When mixed with a-camphorene tetrahydrochloride obtained from the blue camphor oil, the melting-point of this body was not depressed hence the synthetic hydrocarbon is identical with a-camphorene. 

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