No abstract

The reaction between pyridine bases and 2-nitropropane in the presence of iodine is uncomplicated in t-butyl alcohol-water mixtures. In the absence of excess iodide ion and with only a small fraction of the pyridine converted to its conjugate acid, the reversibility can be neglected, and the reaction is apparently free from solvent and lyate ion catalysis. Steric retardation from 2-and 6-alkyl groups in the pyridine is significant, and comparable in magnitude to the acceleration resulting from the increase in base strength. Isotope effects measured when using 2-nitropropane-2-d are large and variable, increasing not only with base strength but also with steric hindrance from a value of kH/kD = 9.8 at 24.88' for pyridine catalysis to kdkD = 24.2 for 2,4,6-trimethylpyridine catalysis at the same temperature. Reasons for the unusually large isotope effects are considered; both tunneling and extensive loss of zero-point energy are invoked.he proton transfer reaction is one of the most im-Py + (CHB)ZCHNO? + Iz ----f PyH' + I-+ (CH&CINO? (1)

No abstract

Many complexes of cobalt in the + 1 oxidation state are excellent nucleophiles. The complex with phthalocyanine, Pcz-, is an example; the rates of reaction of complex (CdPc)-, 1-, with Me1 and other alkylating agents in dimethylacetamide (DMA) solution are reported. In contrast to previous studies with other Co(1) complexes, the rate of reaction of the methylated product, (MeCoII'Pc, 3) with I-is also readily measured, allowing a kinetic evaluation of the equilibriumSimilarly, B r also reacts with 3 reversibly, and the rate and equilibrium constants are reported. Thus 1-is also a good leaving group. With CN, 3 gives complex MeCo*IIPcCNreversibly and slowly gives MeCN in a reaction zero order in CN-. The fast identity rate constants for I-attack on Me1 as well as that for B r attack on Me1 are given. Two different paths to the identity methyl transfer rate constant, kcdo, for the 1-+ 3 reaction with use of the Marcus equation gave kcdo = 4.4 M-I s-1 from the 3 + I-data but kcdo = 0.088 M-I s-1 from the 3 + B r data. This discrepancy, which is outside of experimental error, constitutes a deviation from the Marcus treatment; it is discussed.

No abstract