FATTY ACID ALKYLOLAMIDES By W. B. REINISCH, B.Sc., and K. R. DUTTON, B.Sc., A.R.I.C.* TI•ERF. ARE perhaps few classes of chemical compounds more versatile in use, and important in application to chemists engaged in the field of deter- gency, cosmetics and toiletries, than fatty acid alkylolamides. In view of this it might seem surprising how little is really generally known about the properties and scope of this unique group of substances. One of the chief reasons for this state of affairs may be found in the remarkable lack of published information in this field, which is only gradually and more recently beginning to be remedied. This does not mean, of course, that in actual fact in the laboratories of many companies all over the world the most intensive work is not proceeding in relation to this class of materials. In fact, it is no exaggeration to say that rarely has there ever been such a concentrated drive towards patent protection, as discovery follows discovery in a particular field, as there has been in recent times in connection' with fatty acid alkylo- lamides. Therein probably lies the real reason for the reluctance of most workers to disclose information which might prejudice the chances of patent applications. However, be this as it may be, we feel that sufficient evidence has now been accumulated to say with certainty that fatty acid alkylolamides have come to stay for a long period of time as a potent weapon for the chemist dealing with all kinds of surface-active problems. A further complexity in regard to the fatty acid alkylolamides lies in the fact that, in this field more than in any other, the compounds are frequently offered in the form of relatively impure preparations. This is in part due to the fact that the high reactivity of the alkylolamines makes the prevention of side reactions difficult and therefore, from a commercial standpoint, expen- sive. It is, however, also due to the fact that the impure preparations, or at least those containing "desirable impurities" (which are, perhaps, more accurately described as auxiliary ingredients) are actually more effective than the pure compounds. Thus, for example, complexes of lauric acid diethanolamide and diethanolamine, obtained by condensing at an elevated temperature lauric acid with diethanolamine in an amount in excess of that required for equimolecular proportions, are better wetting agents and detergents than the pure lauric diethanolamide. Indeed, it is even possible to take a pure lauric diethanolamide and improve its wetting characteristics by heating for a period with excess diethanolamine. The practical effect of this situation is that, whereas a chemist can normally buy a chemical compound from one source and expect it to behave, within reasonable limits, * Dutton and Reinisch, Ltd., 130/132 Cromwell Rd., London, S.W. 7. 169

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS similarly to that obtained from another source, in the case of the alkylola- mides he often buys a mixed preparation, which is efficient or otherwise according to its mode of preparation and the skill or lack of it possessed by the manufacturer. Fatty acid alkylolamides can be broadly subdivided into two main classes: (a) freely water-soluble derivatives (b) relatively insoluble waxy materials. The compounds falling within classification (a) are chiefly used as deter- gents (or in some cases foaming agents), as wetting and emulsifying agents, :and as dyeing assistants. Some special examples are used in conjunction with detergents of the alkyl sulphate and alkyl-aryl-sulphonate types, :generally in liquid preparations, to augment the foaming powers of the latter. Compounds falling within class (b) are mainly used as emulsifying agents and emulsion stabilisers, and some particular compounds as additives to various commercially useful detergents to enhance the lathering power and soil removal efficiency of the latter. Recently, certain compounds of this class have been used as dye solvents in cosmetic manufacture. No individual compound will, of course, be ideally suited for all these purposes, and it is a feature of these materials that the product may be "tailor made" for any particular purpose. The critical factor determining in which class a compound would fall is the balance between the hydrophilic "head" (the alkylolamine residue) and the hydrophobic "tail" (the fatty acid chain) of the molecule. In the case of the water-soluble class the "head" generally derives its hydrophilic character in one of three ways. Firstly, the compound may be derived from a simple mono-alkylolamine, but the hydroxyl group of this may be sulphated to give a sulphuric acid ester linkage. Secondly, the fatty acid alkylolamide may be derived from an alkylolamine of greater com- plexity containing more than one hydroxyl group. Thirdly, the fatty acid alkylolamide may be derived from a simple or complex alkylolamine and subsequently condensed with ethylene oxide to increase its water solubility. The sulphated compounds are, of course, anionic detergents. They will in general possess a structure which may be indicated as: R.CO.NH.CH•.CH•... O.SO•Na where R.CO is a fatty acid radical. When R.CO is derived from fatty acids, profusely lathering types of detergents are obtained, which, when correctly manufactured, not only equal lauryl sulphates in most respects, but are superior to them in some, being at the same time far more economically priced. Products based on longer fatty acid chains yield excellent heavy duty detergents with almost unsurpassed lime-soap dispersing properties, but of less profuse lather. Concentrated preparations may be obtained in powder, liquid, or paste form, depending on the particular compound and 170