Straight alkyl chains, number

With bis(3,4,5-trifluorophenyl)-substituted catalyst (S)-16A, the substituent effect of R was examined by changing the number of straight alkyl chains (Figure 5.1). In the asymmetric benzylation of N-(diphenylmethylene)glycine tert-butyl ester 2, use of (CH3(CH2) ,1)2NH (n > 4) gave a uniformly high asymmetric induction. 

Figure 5.1 Effect ofthe number of straight alkyl chains in (S)-16A on enantioselectivity in the asymmetric benzylation of 2.

A straight alkyl chain as the hydrophobic group, rather than a branched alkyl chain containing the same number of carbon atoms. 

The replacement of a straight-alkyl-chain hydrophobic group in POE nonionics by a cycloalkyl or 1-alkylcyclohexyl group with the same number of carbon atoms... 

The physical chemical properties of the surfactants that contain an ester bond between the hydrophobic tail and the polar head group are very similar to those of alcohol ethoxylates of the same alkyl chain length and the same number of oxyethylene units. The CMC and the cloud point values of the linear ester surfactant 1 of Fig. 4 are approximately the same as those of the straight chained alcohol ethoxylate tetra(ethylene glycol)monooctyl ether (C8E4), i.e., around 10 mM and 40 °C, respectively. Thus it appears that the... 

Figure 1. Effect of added straight-chain potassium fatty-acid soaps upon mechanical stability of natural rubber latex (1). Numbers appended to curves are number of carbon atoms in alkyl chain of soap.

Structurally, both compounds contain a 30-carbon straight chain tri and tetrahydroxy carboxylic acid. The alkyl chain in each compound is substituted with an ethyl and a number of methyl groups and two of the hydroxy groups are esterified with two units of tricarballylic acid. One of the methyl groups in actinoplanic acid A is oxidized to an hydroxy methyl group that, in turn, forms a 20-membered 6w-lactone ring with the free carboxy group of one of the tricarballylic acids [86,87]. 

The influence of the nature of the chains on the transition temperatures and mesomorphism was then investigated systematically in order to try to find some correlations between the properties and the structure. This led to a broad study, where the alkoxymethyl chains of the above compounds were replaced by, for example, straight (or branched) alkyl chains, alkoxy chains, thioalkyl chains, octanoate chains, and ethylene oxide chains. The number of chains in the periphery has also been modified for the same purpose. 

The oxidation described here was performed in 80% (v/v) acetonitrile — 20 % water (mole fraction of water = 0.42) at 35.0 °C. Figure 2 shows the selectivity as a function of the number of carbon atoms in R2. In the case of oxidation of la and 2a (R2 = branched alkyl groups), the selectivity reaches a sharp maximum (r = 2.4) at the isopentyl group (j = 2)l8). For R2 = straight-chain alkyl groups, alternation in the selectivity is clearly observed 18). The difference between the r value for la and 2a2 and that for la and 2h2 reaches up to 3.7. 

---