Citral oxime

Citral readily forms acetals by acid-catalyzed addition of alcohols or by the use of trialkoxyorthoformates. Citral dimethyl acetal [7549-37-3] is stable under alkaline conditions, whereas citral is not. Neryl and geranyl nitriles can be made by oximation of citral and dehydration of the intermediate oxime. For instance, geranonitrile [31983-27-4] is made as follows ... 

The products have the characteristic lemon odor of citral and also have greater odor strength and chemical stabiUty than citral. As the need for more stable citms-like fragrances for use in bleach developed, other nitrile compounds have been made available commercially. CitroneUyl nitrile is made from citroneUal dimethyloctanenitrile is produced from dimethyloctanal by the oximation method. 

Aldehydes (e.g., citral, cinnamic aldehyde, etc.) and certain ketones e.g., acetone) react with hydroxylamine hydrochloride forming oximes with the liberation of hydrochloric acid (Z. a., 1895, 623) which can be titrated in presence of methyl orange. 

When citral reacts with hydroxylamine, it yields C10H17ON/ an addition of NH. Since hydroxylamine can react with a carbonyl group to form an oxime by adding an NH, one can suggest that citral contains a carbonyl group. 

Derivatives of ketones and aromatic and unsaturated aldehydes are most easily hydrolyzed. In the case of aliphatic aldehydes the cleavage does not take place so easily. Of course, the substituents of the used hydrazine also play a role. For example, semicarbazones are hydrolyzed with difficulty differences in the reactivity of semicarbazones were successfully applied for the separation of a mixture of a- and ) -citral. For the separation of hydrazones of a-, J -unsaturated aldehydes, oxalic or phthalic acid can be used for easily hydrolyzable oximes, sulfurous acid may serve. More stable hydrazones require mineral acids for their hydrolysis, often concentrated, and also elevated temperatures (79). It is advantageous to carry out the cleavage in an inert atmosphere to prevent unwanted side reactions (80). 

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