Cyclohexyl chloride, reaction

By using a lOOX excess of the metal (less than lOO for experiments on a large scale) one can save much time. Some Grignard reactions, especially those with tertiary alkyl chlorides and cyclohexyl chloride, are not easily started and it seemed desirable, therefore, to inform the user of this book about our experiences. 

Cyclohexyl bromide, for exfflnple, is converted to cyclohexene by sodium ethoxide in ethanol over 60 times faster than cyclohexyl chloride. Iodide is the best leaving group in a dehydrohalogenation reaction, fluoride the poorest. Fluoride is such a poor leaving group that alkyl fluorides are rarely used as starting materials in the preparation of alkenes. 

Finally, reaction of primary, secondary, or tertiary alcohols 11 with Me3SiCl 14 in the presence of equivalent amounts of DMSO leads via 789 and 790 to the chloro compounds 791 [13]. n-Pentanol, benzyl alcohol, yS-phenylefhanol or tert-butanol are readily converted, after 10 min reaction time, into their chloro compounds, in 89-95% yield, yet cyclohexanol affords after reflux for 4 h cyclohexyl chloride 784 in only 6% yield [13] (Scheme 6.5). 1,4-Butanediol is cyclized to tetrahydrofuran (THF) [13a], whereas other primary alcohols are converted in 90-95% yield into formaldehyde acetals on heating with TCS 14 and DMSO in benzene [13b] (cf also the preparation of formaldehyde di(n-butyl)acetal 1280 in Section 8.2.1). 

Phenylnaphthalene has been prepared by the reaction of a-halonaphthalenes with mercury diphenyl3 6 or with benzene in the presence of aluminum chloride,6 and by means of the Gri-gnard synthesis, starting with either bromobenzene, cyclohexyl chloride, and a-tetralone 7 or with a-bromonaphthalene and cyclohexanone.6 8 9 Dehydrogenation of the reduced naphthalene has been accomplished by the use of sulfur,6 bromine,8 platinum black, or selenium.7 The formation of the hydrocar-... 

Halogenation reactions of alkanes provide good examples of radical processes, and may also be used to illustrate the steps constituting a radical chain reaction. Alkanes react with chlorine in the presence of light to give alkyl chlorides, e.g. for cyclohexane the product is cyclohexyl chloride. 

Finally, when we are running out of cyclohexane, the process terminates by the interaction of two radical species, e.g. two chlorine atoms, two cyclohexyl radicals, or one of each species. The combination of two chlorine atoms is probably the least likely of the termination steps, since the Cl-Cl bond would be the weakest of those possible, and it was light-induced fission of this bond that started off the radical reaction. Of course, once we have formed cyclohexyl chloride, there is no reason why this should not itself get drawn into the radical propagation steps, resulting in various dichlorocyclohexane products, or indeed polychlorinated compounds. Chlorination of an alkane will give many different products, even when the amount of chlorine used is limited to molar ratios, and in the laboratory it is not going to be a particularly useful process. 

Problem 11.38 Irradiation of an equimolar mixture of cyclohexane, toluene and Br in CCI4 gives almost exclusively benzyl bromide. A similar reaction with Clj gives mainly cyclohexyl chloride. Explain. ... 

Reaction Chloro- benzene Benzyl chloride Cyclohexyl chloride... 

Substantially the same sulfochlorination reaction has been carried out by Kharasch and Read,166 using S02C12 and light in the presence of substances such as pyridine, which may catalyze the breakdown of S02CI2 into S02 and Cl2. Thus, with cyclohexane, yields of 55% sulfonyl chloride and 10% cyclohexyl chloride are obtained. Similar chlorosulfonations of paraffinic hydrocarbons are described.150... 

The cyclopropyl halides are exceptional in that their behavior is much more like alkenyl halides than like secondary alkyl halides. Thus cyclopropyl chloride undergoes SN1 and SN2 reactions much less rapidly than isopropyl or cyclohexyl chlorides. A relationship between the reactivity of cyclopropyl chloride and chloroethene is not surprising in view of the general similarity between cyclopropane rings and double bonds (Section 12-5). This similarity extends to cyclopropylmethyl derivatives as well. Cyclopropylmethyl chloride is reactive in both SN-1 and SN2 reactions in much the same way as 3-chloropropene ... 

Cyclohexyl chloride 81a reacts with Ph2P ions under irradiation to form 33% of the substitution product. The reaction was strongly inhibited by / -DNB, suggesting that 81a reacts exclusively by the S l mechanism (equation 66)54,151. 

The carbonylation reaction of cyclohexyl chloride and bromide by the dianion Na2Fe(CO)4has been suggested to proceed by the S l mechanism127. 

Relative to tertiary alkyl halides, secondary derivatives react considerably slower. At room temperature and long reaction periods ( 24h) cyclohexyl chloride is almost quantitatively methylated with dimethyltitanium dichloride (prepared in situ from dimethylzinc and catalytic amounts of TiQ4)137>, but other cyclic or acyclic halides tend to undergo competing rearrangements prior to C—C bond formation 77). The same applies to 1,2-dihalides such as 1,2-dibromocyclohexane which affords 1,1-dimethylcyclohexane instead of the 1,2-dimethyl derivative137. In complete contrast, activated secondary chlorides behave much like tertiary derivatives, i.e., methylation is fast and position specific at low temperatures. Examples are shown in Equation 86137>. It should be noted that in such cases cuprate chemistry affords less than 40 % of methylation products138). 

Problem 11.38 Use 4- and — signs for positive and negative tests in tabulating rapid chemical reactions that can be used to distinguish among the following compounds (a) chlorobenzene, benzyl chloride and cyclohexyl chloride (b) ethylbenzene, styrene, and phenylacetylene. ... 

A mixture of 160 g. (1.35 moles) of cyclohexyl chloride and 1.5 1. of benzene is stirred, and a few tenths of a gram of pure anhydrous aluminum chloride is added. After the initial reaction is over, more aluminum chloride is added until a total of about 1.5 g. has been added. The mixture is stirred for 45 minutes and then allowed to stand for 2 hours. The reaction mixture is washed with water, strong aqueous sodium hydroxide solution, and once more with water, then dried over calcium chloride and distilled. Phenylcyclohexane is obtained in 78% yield (190 g.) boiling at 107°/13 or 76°/0.5 mm. 

Support for the c/j-nature of the elimination reaction has come from the work of Barton et on the pyrolysis of menthyl chloride, and the results of this study have recently been confirmed by Bamkole > who also examined the pyrolysis of neomenthyl chloride. The product ratio of menthene-3 to methene-2 is 3 1 in the case of menthyl chloride and 1 6 in the case of neomenthyl chloride, thus demonstrating a preference for m-elimination in each case. These two decompositions do, however, have some unusual characteristics the Arrhenius parameters are considerably lower than those reported for other secondary chlorides, and the rate of elimination of hydrogen chloride from each compound is appreciably faster than from cyclohexyl chloride . (The relative rate of pyrolysis of menthyl chloride and cyclohexyl chloride at 300 °C is about fifty.)... 

There is much additional evidence to support the postulate that the effect of neighboring sulfur is due to anchimeric assistance. Cyclohexyl chloride undergoes solvolysis in ethanol-water to yield a mixture of alcohol and ether. As usual for secondary alkyl substrates, reaction is SnI with nucleophilic assistance from the solvent (see Sec. 14.17). A C5H5S— group on the adjacent carbon can speed... 

Cyclohexylbenzene has been prepared by the hydrogenation of biphenyl and of cyclohexenylbenzene over nickel, by the reaction of cyclohexyl chloride or bromide with benzene in the presence of aluminum chloride, and by the addition of benzene to cyclohexene in the presence of aluminum chloride, sulfuric acid, or boron halides. ... 

REACTIONS CHLOROBENZENE BENZYL CHLORIDE CYCLOHEXYL CHLORIDE... 

All the reactions discussed subsequently show first-order kinetics, and for those systems which have been examined at low pressures, the Lindemann fall-off. The latter are ethyl chloride, n-propyl chloride, isobutyl chloride (Howlett, 1952) and t-butyl chloride (Howlett, 1952 Roberts, 1961), cyclohexyl chloride (Swinbourne, 1958) and isopropyl bromide (Kale and Maccoll, 1964). 

---