A-Chlorocyclohexane

Propose products (if any) and mechanisms for the following AlC -catalyzed reactions (a) chlorocyclohexane with benzene (b) methyl chloride with anisole (c) 3-chloro-2,2-dimethylbutane with isopropylbenzene... 

The flask was charged with 48 g of magnesium and 200 ml of dry diethyl ether. 1,2-Dibromoethane (4 ml) was added. After a few minutes a vigorous reaction started and the diethyl ether began to reflux. When this reaction had subsided, 500 ml of dry diethyl ether were added. Stirring was started and 1.0 mol of chlorocyclohexane (note 1) was added from the dropping funnel at a rate such that the diethyl ether gently refluxed (note 2). After this addition, which was carried out in 1 h, the flask was heated under reflux for a further 1 h. 

Anti periplanar geometry for E2 reactions is particularly important in cyclohexane rings, where chair geometry forces a rigid relationship between the substituents on neighboring carbon atoms (Section 4.8). As pointed out by Derek Barton in a landmark 1950 paper, much of the chemical reactivity of substituted cyclohexanes is controlled by their conformation. Let s look at the E2 dehydro-halogenation of chlorocyclohexanes to see an example. 

On using Barton-oxidation procedures cyclohexane is oxidized by 1949, in the presence of FeCb and the Fe "-picolinate complex, to give cyclohexanone and cyclohexanol [166] whereas with FeCl2 1-chlorocyclohexane is the mayor product, with cyclohexanone and a small amount of cyclohexanol [167] (Scheme 12.47). 

Triphenylmethane leuco dyes are used for photographic materials. The photographic system requires a polymer binder such as acrylic acid-methyl methacrylate copolymer115 or a copolymer of isophthalic and terephthalic acids116 a sensitizer such as 4-(4-n-amyloxyphenyl)-2,6-bis(3-ethylphenyl)-thiapyrilium perchlorate,117 a photo initiator such as hexaarylbisimi-dazole,118 and phenyl tribromomethyl sulfone, cycloalkane such as 1,2,3, 4,5-pentabromo-6-chlorocyclohexane,119 or 3-benzylidene-9-methyl-2,3-dihydro- 1 TZ-cyclopenta [b] quinoline.120... 

Chlorocyclohexane is converted into cyclohexane in dichloromethane using ethyldichlorosilane as reducing agent.192 The product yield is 40% with 25 mol% aluminum chloride and 45% with aluminum bromide. 1-Chloro-l-methylcyclohex-ane gives a 94% yield of methylcyclohexane using aluminum chloride and a 92% yield with aluminum bromide. Ethyldichlorosilane is superior as a hydride donor to either cumene or dicumylmethane.192... 

Lindane, a widespread insecticide constituted of technical mixtures of hexa-chlorocyclohexane (HCH), was dechlorinated using Pd/C, Pt/C, or Raney-Ni. The product using the multiphasic system was benzene, obtained within 1 hour. The base initially promoted HCl ehmination from HCH to yield trichlorobenzene, which then underwent the usual hydrodechlorination reaction. 

It is usual for a coordination compound to write the formula of a ligand with the donor atom first. The nickel complex represented above has both S and P bonded to the metal (as well as all the carbon atoms of the C5H5). The ring structure for chlorocyclohexane should be obvious. 

Problem 13.11 For the following pairs of halides and carbonyl compounds, give the structure of each alcohol formed by the Grignard reaction, (a) Bromobenzene and acetone, (b) p-Chlorophenol and formaldehyde, (c) Isopropyl chloride and benzaldehyde. (d) Chlorocyclohexane and methyl phenyl ketone. 4... 

The nucleophilic displacement of halogens by fluorine can be successfully carried out by reaction with potassium fluoride under several conditions. Primary and secondary alkyl halides 1 are converted to the corresponding fluorides 2 by heating with a saturated aqueous solution of potassium fluoride in the presence of catalytic amounts of hexadecyltributylphosphonium bromide.56 Small amounts of the corresponding alcohol and the olefinic elimination product are formed as side products. While neopentyl bromide does not react at all, polyhaloalkanes give only products of elimination or hydrolysis. Chlorocyclohexane gives only the elimination product.56... 

A convenient method for the chlorofluorination of cyclohexene, with a mixture of lead(IV) acetate and anhydrous hydrogen fluoride in the presence of sodium or copper(II) chloride in 1,1,2-trichlorotrifluoroethane (Halon-113) at room temperature, has been described.22 The major product in this reaction is /ranj-l-chloro-2-fluorocyclohexane obtained in 70% yield. Byproducts are 2-chlorocyclohexanol and l-acetoxy-2-chlorocyclohexane which are obtained in 25 and 5 % yield, respectively. 

The free-radical-induced reaction of alkanes with sulfuryl chloride characteristically results in the chlorination of hydrocarbons. However, when pyridine is added to the irradiated reactants, sulfochlorination occurs in quite satisfactory yield. For example, the irradiated reaction of cyclohexane and sulfuryl chloride in the presence of pyridine resulted in a 54.8% yield of cyclohexanesulfonyl chloride and only 9.4% of chlorocyclohexane.161... 

Fig. 4.4. Carbon-13 shift increments of chlorocyclohexane for rapid (a) and frozen (b) cyclohexane ring inversion (X = Cl).

From many studies it is known that the interconversion of conformations with the substituent in the equatorial and the axial positions occurs about 100,000 times per second, which corresponds to a transition-state energy (activation energy) of about 11 kcal mole-1 above the ground-state energy. The rate decreases as the temperature is lowered. If one cools chlorocyclohexane to its melting point (—44°), the substance crystallizes to give the pure equatorial isomer. The crystals then can be cooled to —150° and dissolved at this temperature in a suitable solvent. At —150° it would take about 130 days for half of the equatorial form to be converted to the axial form. However, when the solution is warmed to —60° the equatorial conformation is converted to the equilibrium mixture in a few tenths of a second. 

When trans-1,2-cyclohexanediol is treated with equimolar TPP in excess CCI4, a 88% yield of trans-2-chlorocyclohexanol can be realized with no evidence ( 11, 1SC NMR, GLC) for trans-1.2-di-chlorocyclohexane or cis-2-chlorocyclohexanol. Since the trans chlorohydrin could not arise from simple displacement of TPPO by chloride ion with retention of stereochemistry (3), we suspected the intermediacy of cyclohexene oxide which could subsequently undergo ring opening by the hydrochloric acid (HC1) generated in solution. This was easily proven by repeating the reaction in the presence of solid potassium carbonate and realizing a 86% yield of cyclohexene oxide and no cis or trans chlorohydrins. 

When 2 equiv (relative to catalyst) of 2,6-di-terf-butylhydroxytoluene (BHT, a radical reaction inhibitor) was added to the reaction, the yield of the reaction decreased by half. A radical trap experiment using cyclohexane was carried out in CCI4 as well, and together with 40% amination product, 12% of chlorocyclohexane was also detected. This result also suggests that a radical pathway is operative. When a 1 2.3 mixture of cis- and trans-2 pentene was reacted with PhI=NTs (Scheme 6.7), a 1 1.5 cis trans aziridine product was isolated, which suggests the mechanism may... 

Write a mechanism for the light-initiated reaction of cyclohexane with chlorine to give chlorocyclohexane. Label the initiation and propagation steps. 

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