and ketones relative to hydrocarbons.20 It is probable that at least part of the deviations arises from subtle differences in conformations. In any event, the heavy dependence of 13C chemical shifts upon steric forces in (20) F.

No abstract

The kinetics of 1,2-dicarba-c/aro-dodecaborane(l2) formation from BioHi2[(CH3)2S]2 and several acetylenes [HC=CCH2Br, HC=CCH20C(=0)CH3, HC=C(CH2)2CH3, HC=C(CH2)sCH3, HC=C(CH2)3C1] have been studied. A mechanism is proposed consistent with the data obtained. AH* and AS* correlate well with the Taft polar substituent constants for the acetylene substituents.A wide variety of substituted 1,2-dicarba-c/oio-dodecaborane(12) derivatives have been synthesized and characterized.2™4 The most common method for their preparation is through the use of diligand derivatives of decaborane, B10H12L2 (L = Lewis base), and acetylenes. Alkyl derivatives are generally prepared in low yields, ca. 30-40%, from the corresponding acetylenes while other derivatives from acetate

Methacrylic polymers and copolymers are noted for their water‐clear color and excellent durability. They are available with a wide range of physical properties which makes them suitable for a broad variety of applications. Physical properties of the important commercial monomers and the polymers they produce are given. The basic principles utilized in the manufacture of methacrylic polymers by free‐radical processes are discussed. These processes include bulk, solution, emulsion, and suspension polymerizations. Graft and anionic polymerizations are also reviewed. Economic, health, and safety perspectives are given. Leading references describing the uses of methacrylic polymers in a variety of applications are noted.

exo-1 (ra = 2). The flask was stoppered and stirred at 41°for 34 hr. Work-up as described above gave 150 mg of a product whose nmr spectrum was consistant with that of known endo-2 (ra = 2) and displayed no exo-2 aldehydic signal at 9.1 ppm.9Air oxidation of the carboxaldehyde gave an acid identical with authentic bicyclo [4.1.0] heptane-7-eracfo-carboxylic acid (4, =