104 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Properties. 



Allyl alcohol is a colourless neutral liquid with an irritating smell 

 and boils at 96-97. It mixes with water, alcohol and ether in all 

 proportions. 



It has the properties of a primary alcohol and of an unsaturated 

 compound, e.g. it reacts with sodium, forms esters and yields acro- 

 lein and acrylic acid on oxidation; it combines with 2 atoms of 

 chlorine or bromine. 



Esters of Allyl Alcohol. 



Allyl iodide. This ester may be prepared from allyl alcohol, but is 

 more conveniently prepared from glycerol by the action of phosphorus 

 and iodine. The glycerol is probably converted into tri-iodide, which 

 decomposes into iodine and allyl iodide. 



It is a colourless liquid boiling at 101 with the odour of garlic. 



Allyl sulphide. Allyl sulphide occurs in garlic and other plants, and 

 is obtained by distilling the plant after it has been macerated with water. 



It may be prepared from allyl iodide by heating with potassium 

 sulphide in alcoholic solution (cf. p. 79). 



It is a colourless, oily liquid boiling at 140 with the smell of garlic 

 and hence is termed oil of garlic. 



Allyl isothiocyanate is a constituent of black mustard seeds and is 

 termed oil of mustard. 



Acrolein. 



Preparation. 



Acrolein is prepared by distilling glycerol (l part) with potassium 

 hydrogen sulphate (2 parts) : 



CH 2 OH CHO 



CHOH = CH + 2H a O 



CH 2 



The smell of acrolein is noticed on heating a few drops of glycerol in a 

 dry test tube with anhydrous phosphoric acid or acid potassium sulphate. 



Properties. 



Acrolein is a colourless liquid boiling at 52, with a most irritating 

 and peculiar odour ; it affects the eyes, producing tears, and it forms 

 sores upon the skin. 



It has the reactions of an aldehyde, but does not combine with 

 sodium bisulphite, and also the reactions of unsaturated compounds. 



