Propyl halides

The complex nature of alkylation of alkenes is illustrated by the reaction of 1- and 2-chloropropane with ethylene,53 which does not yield the expected isopentyl chloride. Instead, l-chloro-3,3-dimethylpentane is formed by isomerization of the primary product to give fcrf-amyl chloride, which adds to ethylene more readily than do starting propyl halides (Scheme 5.4). The same product is also obtained54 when ethylene reacts with neopentyl chloride in the presence of AICI3. 

Subsequent work by Bedos,equally applicable to cyclohexene oxide (Eq. 917), which yielded tla-corresponding jS-haloethers on treatment with methyl, ethyl, or n-propyl halides at 160-190 . The stereochemical course of the reaction was of course not explored at the time, but may be supposed to lend t-n a frans-ooufigur tiou. 

Dihaloethanes are usually slightly less reactive toward nucleophiles than, for example, the corresponding propyl halides [155], Although several successful nucleophilic substitutions at 1,2-dichloroethane or 1,2-dibromoethane have been performed (Section 10.6), several examples of poor results with these electrophiles have also been reported (Scheme4.39). 

With an w-propyl halide and an allyl halide as the alkylating agents, the acetoacetic ester syn- allyl group... 

N-Alkylation of 3-aroylindole 97 carried out at 80 °C with alkyl halides from ethyl through -hexyl, gives mixtures of products 98 and 99 in yields of 41-90% (Equation 15) <1998JOC4510>. In addition to the expected N-alkylated indoles 98, a substantial fraction of the product was formed by additional replacement of the methoxy group by an alkoxy group. The reaction is very temperature dependent, since a decrease of only 5 °C completely suppresses the formation of the 0-alkylation products with the ethyl or -propyl halide. However, -hexyl bromide provided a 75% yield of hexyl ether 99 under these conditions. 

Pentanes and Hexanes.—In exactly the same way in which we have explained the isomerism in the case of the propyl halides and butanes we are able to explain that of the pentanes and hexanes. The number of possible isomeric hydrocarbons naturally increases as the number of carbon atoms increases. Three isomeric hydrocarbons of the formula C5H12 are possible and three are known, and five of the formula CeH, all likewise being known. 

A sequence starting with methylenebis[phosphonic acid] tetraester carbanions, and consisting of alkylation with an appropriate 3-substituted-propyl halide, side-chain modification, and cyclization, ultimately affords the tetraalkyl esters of cyclopropane-1,l-bis[phosphonic acid], and from which the free acid has been obtained.The reaction between 1,2-dibromoethane and ethyl (diethoxyphosphinyl) acetate or ethyl... 

This in turn depends upon the alkane and which hydrogen atom is abstracted from it. For example, w-propyl halide is obtained from a //-propyl radical, formed from propane by abstraction of a primary hydrogen isopropyl halide is obtained from an isopropyl radical, formed by abstraction of a secondary hydrogen. 

Propylene could yield either of two products, the /7-propyl halide or the isopropyl halide, depending upon the orientation of addition, that is, depending upon which carbon atoms the hydrogen and halogen become attached to. Actually, it is found that the isopropyl halide greatly predominates. 

SOLUTION The sp carbons of 4-decyne are bonded to a propyl group and to a pentyl group. Therefore to obtain 4-decyne, the acetylide ion of 1-pentyne can react with a pentyl halide or the acetylide ion of 1-heptyne can react with a propyl halide. Since 1-pentyne is not available, the chemist should use 1-heptyne and a propyl halide. 

The Williamson ether synthesis is a nucleophilic substitution reaction. It is an Sn2 reaction because it requires a high concentration of a good nucleophile. If you want to synthesize an ether such as butyl propyl ether, you have a choice of starting materials You can use either a propyl halide and butoxide ion or a butyl halide and propoxide ion. 

In ethanol containing ethoxide, the threo and erythro isomers of 1,2-diphenyl-1-propyl halides or trimethylammonium ion react in a similar stereochemical fashion , but in r-butyl alcohol containing r-butoxide, both the ammonium salts give the tra/i -olefin under kinetically controlled conditions . As both isomers have similar thermodynamic stabilities and react at similar rates, the anticipated comparable energies of the transition states have been attributed to the possible incursion of the ElcB mechanism . This seems unlikely as in the analogous elimination from the 2-phenylethyltrimethyl-... 

Other Lewis acid/oxidant systems have been employed including ASFj/AsFj [100] and liquid SO2 or sulfuric acid and aluminum chloride [101]. Poly(paraphenylene) has been synthesized by the electrochemical oxidation of benzene in solvents such as liquid SO2 [102] and concentrated sulfuric acid [103], or with the addition of Lewis acids including aluminum chloride [104], CuCl2/LiAsFg [105], and BF30Et2 [106], affording polymeric films. To improve the solubility, poly(paraphenylene) has been sulfonated [107] and alkylated [108] with propyl halides to give materials with enhanced solubility. 

When we are considering a question involthng reaction rates, the answer can always be found through an analysis of the transition states. The rate is dependent on the activation energy for the reaction, which is the height of the transition state relative to the starting halide. Let s compare the transition state for the reaction of a 1-propyl halide with that for the reaction of an allyl halide (Fig. 12.49). 

Hexanone can be synthesized from 3-hexanol, which can be synthesized from a three-carbon aldehyde and a three-carbon Grignard reagent. Oxidation of 1-propanol forms the three-carbon aldehyde, and conversion of 1-propanol to a propyl halide allows the three-carbon Grignard reagent to be synthesized. 

Preparation by partial alkylation of 4 -fluoro-2,4-di-hydroxybenzophenone with a propyl halide in the presence of an alkali [1109],... 

An aq. soln. of 2-allyl-l,3-cyclohexanedione (prepn. s. Synth. Meth. 9, 893) and NaOH hydrogenated with Raney-Ni until the calculated amount of Hg has been absorbed 2-propyl-l,3-cyclohexanedione. Y 85%.—This 2-step synthesis is more advantageous for the prepn. of larger amounts than the direct alkylation with propyl halides. H. Stetter, R. Engl, and H. Rauhut, B. 91, 2882 (1958). 

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