ETHYLENIC HYDROCARBONS ALKENES Amylene

Amylene is a general name for the ethylenic hydrocarbons of the molecular formula C5H10. Two of these hydrocarbons are the main products of the dehydration of the appropriate amyl alcohols  

Tertiary alcohols are more readily dehydrated than secondary alcohols, whilst primary alcohols are dehydrated with comparative difficulty. Thus the reaction proceeds easily with 33 per cent, sulphuric acid (1 acid 2 water, by volume) for tert.-amyl alcohol, but 50 per cent, (by volume) is required for aec.-amyl alcohol. Higher concentrations of acid tend to lead to increasing polymerisation of the olefine and are therefore usually avoided. 

2-Pentene. Proceed as in A, but use the following quantities 50 ml. of water and 50 ml. of concentrated sulphuric acid 40 g. of methyl n-propyl carbinol (4). Collect the distillate passing over below 40°. Pure 2-pentene boils at 36-5°. 

A general method for the synthesis of 1-alkenes is provided by the action of a Grignard reagent upon allyl bromide, for example  

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