Hydroxyl group, secondary, compared

On treatment with acrylonitrile in 2% aqueous sodium hydroxide at 0°, tetrahydropyran-2-yl /3-D-glucopyranoside gave the 2-, 3-, 4-, and 6-0-(2-cyanoethyl) ethers (together with some diethers) in yields that, on extrapolation to zero reaction, showed3 9 k2 k3 k4 k6 to be in the ratios of 3 1 2 8 these values represent equilibrium, not rate, constants. The tendency for substitution at 0-6 is a consequence of the greater stability of an ether derived from a primary (compared to a secondary) hydroxyl group, as a result of lower steric interactions in the former. 

Sunamoto et al. 94) have studied the reaction of (14) with 2,4-dinitro-phenyl sulfate in aqueous organic solvent with 0.1 A sodiiun hydroxide. The rate of esterolysis by (14) was greater than the rate of the reaction catalyzed by -cyclodextrin. Better binding by the paracyclophane cavity and the greater nucleophilicity of the oxime group as compared to the secondary hydroxyl group of jS-cycdextrin were cited to explain the difference in catalytic efficiency. 

Cellulose Triacetate. Cellulose acetate having 92% or more of the hydroxyl groups acetylated is referred to as triacetate. This fiber is characteristically more resistant to alkali than the usual acetate and may be scoured, generally, in open-width, with aqueous solulions of a synthetic surfactant and soda ash. Triacetate is a hydrophobic liber, as compared to secondary acetate, and consequently does not dye rapidly. It is necessary to increase the rate of diffusion of the disperse dye into the fiber by increasing the dyeing temperature to 110— 130CC or using a dye accelerant or carrier, or both. 

The enhanced reactivity of the 2-hydroxyl as compared to other secondary hydroxyl groups has been noted primarily in reactions requiring alkaline media. This effect is probably a result of the greater acidity of hydroxyl groups adjacent to a carbonyl or a potential carbonyl group. 

The perchlorates of various secondary amines, such as diphenylamine and indole derivatives, are colorless.64 The similarity of colors produced in the presence of hydrochloric acid also attests to the non-auxochromic character of the perchlorate ion in the production of the colored derivative. Consequently, the only role attributable to the perchloric acid in this test is that with nucleic acids it leads to more effective hydrolysis and releases more 2-desoxyribose for reaction with tryptophan. This reaction leads to the production of a substance of the type represented by XV and XVI (R " = H), and the increase in the number of conjugated double bonds results in the product being colored. With ribose, which has a free hydroxyl group at carbon atom 2, a ketone of the type shown in XVII can be formed, and in this case the net result is no increase in the number of double bonds conjugated with the indole nucleus and no comparable increase in color. Hence the test will distinguish between ribose and 2-desoxyribose. 

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