Degree of alkyl substitution

The first step in this preparation, the epoxidation of 1,4,5,8-tetra-hydronaphthalene, exemplifies the well-known selectivity exerted by peracids in their reaction with alkenes possessing double bonds that differ in the degree of alkyl substitution.12 As regards the method of aromatization employed in the conversion of ll-oxatricyclo[4.4.1.01-6]-undeca-3,8-diene to l,6-oxido[10]annulene, the two-step bromination-dehydrobromination sequence is given preference to the one-step DDQ-dehydrogenation, which was advantageously applied in the synthesis of l,6-metliano[10]annulene,2,9 since it affords the product in higher yield and purity. 

Measurements of the surface tension of aqueous solutions of various sulphonated and unsulphonated phenylazonaphthol dyes showed that the degree of surface activity (that is, the lowering of surface tension) tended to increase progressively with the degree of alkyl substitution in the series of dyes [7]. The surface-active behaviour of such alkylated dye ions ensures that they become more concentrated at the interface between the dyebath and the fibre surface, just as they do at the air-water interface of the dye solution. Foaming of dyebaths can be a serious practical problem with relatively hydrophobic dye structures solubilised by means of a single ionised group. 

The reduction of dienes by diimide depends on the nature of the substitution of the diene. Several studies of relative reactivity have been carried out and they indicated that an increasing degree of alkyl substitution on the double bond results in decreasing reactivity82. In the case of allenes, the reduction of the less substituted allenic double bonds and the formation of the thermodynamically less stable cis olefin can be explained by the steric control of the approach of the diimide (equation 23)83. 

Aromatics react with olefins very readily when potassium is used as a catalyst. However, potassium is less selective in catalyzing alkylation than sodium because an additional reaction yields indans, as reported by Schaap and Pines 24). Therefore, the products consist of mixtures of arylalkanes and indans the relative amount of each depends largely on the aromatic used (as shown in Table II). The degree of alkyl substitution of the o -carbon... 

The names of the secondary-butyl (sec-butyl) and tertiary-butyl (ferf-butyl or f-butyl) groups are based on the degree of alkyl substitution of the carbon atom attached to the main chain. In the, vec-butyl group, the carbon atom bonded to the main chain is secondary (2°), or bonded to two other carbon atoms. In the ferf-butyl group, it is tertiary (3°), or bonded to three other carbon atoms. In both the n-butyl group and the isobutyl group, the carbon atoms bonded to the main chain are primary (1°), bonded to only one other carbon atom. 

There are four possible degrees of alkyl substitution for carbon. 

In these studies, the same fossil-derived crudes were used as described in the alkane fractionation work, i.e., two coal liquids, a shale oil, a petroleum, and a petroleum blend. Estimates of PAH components showed the highest overall amounts in shale oil and in one of the coal liquids. The petroleums contain the least amount and are comparable with the other coal liquid in this respect. Also, the petroleums have little detectable material of more than three rings, while the coal liquids contain appreciable quantities of five-six-ring PAH. Shale oil PAH compounds are predominantly in the 2-3-ring class with a high degree of alkyl substitution. 

One further word about naming alkyl groups The prefixes sec (for secondary) and tart (for tertiary) used for the alkyl groups in Figure 3.3 refer to the degree of alkyl substitution at the branching carbon atom. There... 

Resin lib, which proved somewhat less hydrophilic than the DMH-based resin mixture (see Table VIII), was studied with certain solvents only, as shown in Table XIII. Its lyophobicity was somewhat less than the DMH-based mixture, and in the two aqueous media it was somewhat less affected. Thus, again, its behavior reflected the intermediate degree of alkyl substitution. 

The molecular weight of the different blocks can be controlled by adjusting the polymerization time and the substitution pattern (degree of alkyl substitution) of the monomers and macro monomers. 

The effect of varying degrees of alkyl substitution (mono-, di-, and tri-) in 1,2- and 1,3-dithiolium salts on electronic spectra, charge-transfer spectra with iodide anion as donor, and n.m.r. spectra, has been studied, and the data have been compared with the results of SCF MO calculations. ... 

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