Critical methylene group number

To understand micelle formation quantitatively, critical micelle concentrations (cmc) have to be determined for a large number of surf actants ( 5 ). When the cmc values of the surfactants with the same hydrophilic group (a homologous series) are examined, a nearly 3-fold decrease in cmc is observed for nonlonlc and zwitterionlc surfactants (1,2) upon the addition of a methylene group into the hydrocarbon chain, whereas, a 2-fold or only 1.8-fold reduction in cmc can be observed for univalent (1,2) and blvalent( ) ionic surfactants,respectively. 

The critical test of any model is the capability to reproduce experimentally observed correlations between the mass of an ion and its mobility and between temperature and mobility, as well as to predict the mobility coefficients of ions in different gas atmospheres accurately. Normally, the success of a model is examined with relatively simple systems such as a homologous series of ions. For example, one such series is that in which the only changes arise from the addition of methylene groups in the ion with minimal changes in ion size and internal charge distribution. A complication in this discussion is the limited number of such tests with ions and gases representative of analytical IMS conditions. 

The hydroxylation theory of Bone2 and his co-workers has had wide acceptance as far as the oxidation of aliphatic hydrocarbons is concerned. The mechanism postulated involves the successive formation of hydroxyl compounds, which may add oxygen to form additional hydroxyl groups or which may lose water and decompose. In this way methane would first form methanol, then methylene glycol which would be decomposed to formaldehyde and water formaldehyde would be oxidized to formic acid or decomposed to carbon monoxide and hydrogen. The theory, however, is open to a number of criticisms. 

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