Steam Distillation Isolation of Citral from Lemon Grass Oil

6 STEAM DISTILLATION ISOLATION OF CITRAL FROM LEMON GRASS OIL 

Citral is a naturally occurring oil mainly comprised of two isomeric imsaturated aldehydes, geranial (1) and neral (2), that are extremely difficult to separate. These isomers differ only in the spatial orientation of the substituents about the carbon-carbon double bond that bears the aldehyde moiety (-GHO). This qualifies 1 and 2 as stereoisomers and more specifically as diastereomers, the definitions of which are found in 

Section 7.1. In addition, they are sometimes also called geometric isomers, an older term that is used to describe stereoisomers that differ because the three-dimensional distribution of their substituents is the result of a double bond. 

Citral possesses a lemonlike odor and taste. Although this odor and taste is pleasant to humans, it is less attractive to other species. For example, ants secrete citral to ward off potential predators, so citral is functioning as a defense pheromone. There are several commercial applications of citral. For example, it 

The commercial importance of citral has stimulated an extensive search for its presence in nature. One source is the oil from the skins of lemons and oranges, although it is only a minor component of this oil. However, citral is the major constituent of the oil obtained from lemon grass, and in fact 75-85% of the crude oil derived from pressing lemon grass is this natural product. 

---