106-94-5 1-Bromopropane

Amino-A.-selenazoline and its 5-methyl derivative have previously been obtained by Baringer (61) starting from 2-bromoethylamine hydrobromide and l-amino-2-bromopropane hydrobromide, respectively, by reaction with potassium selenocyanate. 

To a stirred suspension of 5 parts of N-(4-chlorophenyl)-N-(4-piperidinyl)benzeneacetamide, 5 parts of sodium carbonate, a few crystals of potassium iodide in 200 parts of butanol is added dropwise 4 parts of 2-bromopropane at room temperature. After the addition is complete, the whole is stirred and refluxed for 20 hours. Then the second portion of 4 parts of 2-bromopropane is added and stirring and refluxing is continued for another 19 hours. The reaction mixture is cooled, filtered and the filtrate is evaporated. From the oily free bese, the hydrochloride salt is prepared in the conventional manner in 1,1 -oxybisethane and 2-propanone. The precipitated solid salt is filtered off and crystallized from a mixture of 2-propanone and 2-propanol, yielding 2 parts of N-(4-chlorophenyl)-N-[1-(1-methylethyl)-4-piperidinyl] benzeneacetamide hydrochloride melting point 263°C. 

Figure 13.15 The 1H NMR spectrum of 2-bromopropane. The -CH3 proton signal at 1.71 <5 is split into a doublet, and the -CHBr- proton signal at 4.28 8 is split into a septet. Note that the distance between peaks—the coupling constant—is the same in both multiplets. Note also that the outer two peaks of the septet are so small as to be nearly lost.

Elimination reactions involve loss of two substituents from adjacent atoms as a result unsaturation is introduced. In many instances additional reagents are required to cause the elimination to occur, reducing the overall atom economy still further. A simple example of this is the E2 elimination of HBr from 2-bromopropane using potassium -butoxide (Scheme 1.12). In this case unwanted potassium bromide and /-butanol are also produced reducing the atom economy to a low 17%. 

Some data on the alkylation of naphthalene by 2-bromopropane using A1C13 under different conditions are given below. What factors are responsible for the differing product ratios for the two solvents, and why does the product ratio change with time ... 

As we have seen already (p. 104) secondary carbocations are more stable than primary, and in so far as this also applies to the transition states that precede them, (24) will be formed in preference to (23). In fact it appears to be formed exclusively, as the only addition product obtained is 2-bromopropane (25). Addition, as here, in which halogen (or the more negative moiety of any other unsymmetrical adduct) becomes attached to the more highly substituted of the two alkene carbon atoms is known as Markownikov addition. 

The addition of HBr to propene, MeCH=CH2 (63), under polar conditions to yield 2-bromopropane, has already been referred to... 

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