Cyclopropyl chloride

Methylcyclopropane shows strikingly different reactivity toward chlorination and bromination under radical-chain conditions. With chlorine, cyclopropyl chloride (56%) is the major product, along with small amounts of 1,3-dichlorobutane (7%). Bromine gives a quantitative yield of 1,3-dibromobutane. Offer an explanation for the difference. 

Cyclopropyl chloride has been prepared by the free-radical chlorination of cyclopropane. Write a stepwise mechanism for this reaction. 

We admit to presenting no benzene counterpart for gew-disubstituted cyclopropanes. Then again, there are almost no thermochemical data with which to make comparisons save for the three dimethylcyclopropanes. For example, the enthalpy of formation of 1,1-dichlorocyclo-propane is available as are those of the three dichlorobenzenes, but we lack thermochemical data for the monosubstituted cyclopropyl chloride and for both 1,2-dichlorocyclopropanes. 

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 ... 

The amphetamine analog of CPM should be easily made from the alkylation of syringaldehyde with cyclopropyl chloride, followed by conventional reaction of the resulting aldehyde with nitroethane, and finally a reduction step. There is no reason to believe that the resulting compound 3,5-dimethoxy-4-cyclo-propyloxyamphetamine (3C-CPM) would be any shorter acting than CPM. 

Cyclopropane Chlorine Cyclopropyl chloride Hydrogen chloride... 

In this 3-phcnylalkyne system the triple bond becomes incorporated into a cyclo-propene ring, whereas from the enynes 10 and 11 there is no sign of a vinylcyclo-propene product. The preference for reaction to take place at the alkene unit rather than at the alkyne unit in the photochemistry of enynes is seen again in the photochemistry of enepoly-yne chlorides, where only cyclopropyl chlorides are produced (equation 18). This preference is probably a reflection of the lower strain energy in a cyclopropane than in a cyclopropene ring. 

Cyclopropyl chloride has a dipole moment of 1.76 D compared with 2.04 D in cyclopentyl chloride L... 

In order to accomplish a total dehalogenation to hydrocarbons, dissolving metal reductions are most commonly employed. Cyclopropyl chlorides and bromides are satisfactorily reduced by alkali metal in alcohoF or in liquid ammonia. However, the fluorides are usually resistant to the hydrogenolysis. gem-Difluorides have been... 

Many cyclopropyl chlorides and bromides have been converted to alkoxycyclopropanes by treatment with a strong base, in most cases potassium rerf-butoxide, in an appropriate organic solvent (Table 13). Under such conditions, hydrogen halide elimination takes place, yielding strained cyclopropene intermediates, which are trapped by nucleophilic attack of the alkoxide. Overall, a simple substitution occurs when a bond is formed between the alkoxide group and the carbon atom to which the halide was attached. This is the case when l-chloro-5-methyl-exo-6-phenyl-3-oxabicyclo[3.1.0]hexan-2-one (1) was reacted with potassium /ert-butoxide l-/er/-butoxy-5-methyl-ent/o-6-phenyl-3-oxabicyclo[3.1.0]hexan-2-one (2) was isolated in 94% yield.If a C-O bond is established at the other olefinic carbon atom, a C H bond is concomitantly formed at the carbon atom, to which the halide was attached. The result is a double substitution which is discussed elsewhere (see Section 5.2.1.3 ). When the substrate contains more than one halogen atom, several elimination reactions usually take place. Thus, treatment of 1 -bromo-2-chloro-2-methylcyclopropane (3) with an excess of potassium /er/-butoxide gave l-ter/-butoxy-2-methylenecyclopropane (4) in 30% yield. 

Cyclopropyl chlorides can also be converted in a similar fashion to cyclopropylsilanes, but other substituents attached to the ring may react concomitantly. Thus, when l-chloro-l-(l,2,2-trichlorovinyl)cyclopropane reacted with magnesium in a mixture of chlorotrimethylsilane and tetrahydrofuran, 1-trimethylsilyl-l-(2-trimethylsilylethynyl)cyclopropane (9) was obtained in good yield.A C-Si bond was also formed when l-chloro-2-ethylcyclopropanecarboxylic acid was treated with rcrt-butyllithium followed by chlorotrimethylsilane rerr-butyl 2-ethyl-l-(trimethylsilyl)cyclopropanecarboxylate was obtained in 69 % yield. 

The most general entry into functionalized sulfur-containing cyclopropanes is the addition reactions of cyclopropanones and thiols (see Section 5.2.3.5.4.). Thus, reaction of cyclo-propanone with thiols in dichloromethane affords l-(alkylsulfanyl)cyclopropanols 39 which are readily transformed into the corresponding cyclopropyl bromides 40 and cyclopropyl chlorides 41 upon reaction with anhydrous hydrogen bromide and hydrogen chloride, respectively. ... 

Butenyl)-2,2-dimethyl-cyclo-propyl]- -chloride 1285 [3.3-Dimelhyl-2-(2-methyl-allyl)-cyclopropyl]- -chloride 1285... 

Dimethyl-2-(3- methyl-3-buten-yl)-cyclopropyl]- -chloride 1285 C, H CIN,0 3-Aza-bicyclo 3,l, 0 hexane 1 -Chloro-3-methyl-6-morpholino- 909... 

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