There is a possibility, in the reaction to use different alkyl halides instead of a single halide. If two different halides are taken with the aim of preparing an alkane with odd number of carbon atoms, a mixture of products is obtained instead of a single alkane which is difficult to separate. This is because in this case three reactions takes place and three different products are obtained.

for example CH3Br+C2H5Br------->CH3-CH3 +NaBr

                                         -------->CH3-C2H5 +NaBr

                                         --------->C2H5-C2H5+NaBr