The products formed in the direct substitution of alkanes with halogens can be seperated by
fractional distillation
Saturated carbon compounds undergo substitution reactions in the presence of sunlight. For e.g. methane undergoes substitution reaction to form different types of products. Alkanes react with chlorine, bromine or iodine in the presence of sunlight or ultraviolet light to give halogen substituted products that are known as alkyl halides.
They can be separated by fractional distillation.