A kinetic study of the aminolysis of [methoxy (phenyl)carbene]pentacarbonylchromium(0) with five primary aliphatic amines in 20% acetonitrile-80% water (v/v) at 25 °C is reported. Second-order rate constants (kA) increase with amine and OH" concentration, which indicates general base catalysis. Plots of kA vs amine or OH" concentration are curved and level off at high concentration; this implies a change in rate-limiting step and demonstrates that the reaction is stepwise. The mechanism is similar to that for ester aminolysis, i.e., the first step is nucleophilic addition of the amine to the substrate to yield a zwitterionic tetrahedral intermediate (TA*), followed by deprotonation of TA± to form TA" which, in a third step, is converted to products by general acid catalyzed methoxide expulsion. In contrast to ester aminolysis, where general base catalysis is a consequence

Aliphatic amines react with phosphoimidazolide-activated derivatives of guanosine and cytidine (ImpN) by replacing the imidazole group. The kinetics of reaction of guanosine 5'-phospho-2-methylimidazolide (2-MeImpG) with glycine ethyl ester, glycinamide, 2-methoxyethylamine, n-butylamine, morpholine, dimethylamine (Me2NH), ethylmethylamine (EtNHMe), diethylamine (Et2NH), pyrrolidine, and piperidine were determined in water at 37 degrees C. With primary amines, a plot of the logarithm of the rate constant for attack by the amine on the protonated substrate, log kSH(A), versus the pKa of the amine exhibits a good linear correlation with a Bronsted slope, beta nuc = 0.48. Most of the secondary amines tested react with slightly higher reactivity than primary amines of similar pKa. Interestingly, some secondary amines show substantially lower reactivity than might be expected: EtNHMe reacts about eight times, and Et2NH at least 100 times, more slowly than Me2NH although all three amines are of similar basicity. For comparison, the kinetics of reaction of guanosine 5'-phosphoimidazolide (ImpG) and cytidine 5'-phosphoimidazolide (ImpC) were determined with Me2NH, EtNHMe, and Et2NH, and similar results were obtained. These results establish that the increased steric hindrance observed with the successive addition of ethyl groups are not due to any special steric requirements imposed by the guanosine or the methyl on the 2-methylimidazole leaving group of 2-MeImpG. It is concluded that addition of ethyl and, perhaps, groups larger than ethyl dramatically increases the kinetic barrier for addition of aliphatic secondary amines to the P-N bond of ImpN. This study supports the observation that the primary amino groups on the natural polyamines are at least 2 orders of magnitude more reactive than the secondary amino groups in the reaction with ImpN.

Rates of reversible carbon deprotonation of 2-nitroethanol (2) and 2-nitro-1,3-propanediol (3) by hydroxide ion, water, amines, and carboxylate ions and p values for the ionization at carbon (pA^H) and oxygen (pK^H) and ionization of the aci-forms (pK^0H) were determined in aqueous solution at 25 °C. The pÁ^H values for 2 and 3 are 8.60 and 7.68, respectively, as compared to 10.22 for CH3NO2. The acidifying effect of the CH2OH groups is attributed to a combination of inductive electron withdrawal and hyperconjugative stabilization of the respective nitronate ions, possibly coupled with intramolecular hydrogen bonding stabilization of this ion. The higher acidity of 2-nitroethanol compared to nitromethane is reflected in higher rates of proton transfer from 2-nitroethanol, implying a "normal" Brpnsted a between 0 and 1. This contrasts with the negative a value based on the reaction of OH" with nitromethane, nitroethane, and 2-nitropropane (Kresge, A. J. Can. J. Chem. 1974, 52, 1897). Reasons why a normal a value is observed in the current system are discussed.

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[9044][9045][9046][9047][9048][9049][9050][9051][9052] nucleophiles, we can predicate the strength of the hydrogen bond from the electron orbital occupancy of the remote nitrogen. For those proteins studied by ESEEM, we suggest that the histidine ligands of Cu(1l) sites in stellacyanin and dopamine &hydroxylase form strong hydrogen bonds, while for galactose oxidase, amine oxidasc, and phcnylalanine hydroxylase a much weaker or no hydrogen bond is present. Acknowledgment.Abstract: Reactions of anions with acrylonitrile, acrolein, methyl vinyl ketone, and methyl acrylate at room temperature under SIFT conditions are described. Stabilized carbanions such as benzyl anion, cyanomethyl anion, cyclohexadienide, acetone cnolate, and nitromethyl anion add to activated carbon-carbon double bonds in a process that is competitive with other modes of rcaction. With acrylonitrile and methyl acrylate, addition is in a 1,4 or Michael fashion, while with acrolein and methyl vinyl ketone, I ,2 addition competes with I ,4 addition. Hydroxide, methoxide, fluoride, and cyanide do not add to activated olcfins by cithcr mode (see Tables I-IV). A mechanism is proposed for hydride transfer from cyclohexadienide to activated olcfins.Reaction of anions with neutral organic molecules in the gas phase givcs rise to a wide variety of products, including those that can be ascribed to the processes of proton transfer,' elimination,* substituti0n.j and attack at the carbon of carbonyl groups! Using activatcd olefins such as acrylonitrile (1). acrolein (2), methyl vinyl ketonc (3), and methyl acrylate (4) presents the opportunity for CH,=CHCN CH,=CHCHO CH,=CHCOCH, CH,=CHCOOCH, ~~ ~~~~~~~~~~~~~ ( I ) (a) Pellerite, M. J.; Brauman, J. 1. In Camprehensioe Carbanion Chemistry-Part A , Structure and Reactiuity; Buncel, E., Durst, T., Eds.; Elsevier: Amsterdam, 1980. (b) Moylan, C. R.; Brauman, J. 1. Annu. Reo. Phys. Chem. 1983, 34, 187-215. (2) (a) Bartmess. J. E.; Hays, R. L.; Khatri. H. N.; Misra, R. J.; Wilson, S. R. J . Am. Chem. Sac. 1981, 103,4746. (b) DePuy, C. H.; Bierbaum, V. M. J . Am. Chem. SOC. 1981,103,5034-5038. (c) DePuy, C. H.; Beedle, E. C.; Bierbaum, V. M. J. Am. Chem. Sac. 1982,104,6483. (d) Bierbaum, V. M.; Filley, J.; DePuy, C. H.; Jarrold, M. F.; Bowers, M. T.