Dihydrogen-bond-promoted catalysis: catalytic hydration of nitriles with the indenylruthenium hydride complex (eta(5)-C(9)H(7))Ru(dppm)H (dppm = bis(diphenylphosphino)methane)

The indenylruthenium hydride complex (eta(5)-C(9)H(7))Ru(dppm)H was found to be active in catalyzing the hydration of nitriles to amides. The chloro analogue (eta(5)-C(9)H(7))Ru(dppm)Cl was, however, found to be inactive. Density functional theory calculations at the B3LYP level provide explanations for the effectiveness of the hydride complex and the ineffectiveness of the chloro complex in the catalysis. It is learned that the presence of a Ru-H.H-OH dihydrogen-bonding interaction in the transition state lowers the reaction barrier in the case of (eta(5)-C(9)H(7))Ru(dppm)H, but in the chloro system, the corresponding transition state does not contain this type of interaction and the reaction barrier is much higher. A similar dihydrogen-bond-promoting effect is believed to be responsible for the catalytic activity of the hydrotris(pyrazolyl)borato (Tp) ruthenium complex TpRu(PPh(3))(CH(3)CN)H in CH(3)CN hydration. The chloro analogue TpRu(PPh(3))(CH(3)CN)Cl shows no catalytic activity.     

A State-selected study of the symmetric charge transfer reaction H2+ + H2

We have measured the relative total charge transfer cross sections of H₂⁺ + H₂ as a function of the vibrational state of H₂⁺, υ′_o = 0–4. using the crossed ion-neutral beam and high-resolution photoionization methods. The experimental results obtained at a center-of-mass collisional energy of 22.5 eV are found to be in excellent agreement with a recent theoretical study.     

Isolation and determination of p-hydroxybenzoylcholine in traditional Chinese medicine Semen sinapis Albae

A special component is isolated from Semen sinapis Albae (white mustard seed), a traditional Chinese medicine. According to the physical and chemical investigation and spectroscopic identification, this component can be known as p-hydroxybenzoylcholine bisulfate, a choline base. This component in the drug is also determined by RP-HPLC. A reversed-phase C₁₈ column is used to separate the p-hydroxybenzoylcholine with an eluent of methanol–0.05 mol/L monopotassium phosphate solution (30:70) (adjusted by phosphoric acid to pH 3.6) at the flow rate of 0.5 mL/min. Detection is carried out with a UV detector operated at 285 nm, and the column temperature is 25 °C. It reveals that there is 0.021% (w/w) of p-hydroxybenzoylcholine bisulfate in Semen sinapis Albae and 0.037% (w/w) in stir-baked Semen sinapis Albae.     

Total synthesis of (+/-)-herbertenolide by stereospecific formation of vicinal quaternary centers in a crystalline ketone

[reaction: see text] The sesquiterpene (+/-)-herbertenolide was synthesized in seven steps from commercial 2-bromo-4-methylanisole. In the key step, two adjacent stereogenic quaternary centers were controlled by a highly chemoselective and stereospecific photodecarbonylation reaction of crystalline methyl-trans-3-(2-methyl-5-methoxyphenyl)-1,3-dimethyl-2-oxocyclohexancarboxylate (3). An efficient generation of radical pairs and the stereochemical control exerted by the solid state suggest that this reaction may become a useful synthetic method.     

Persulphate initiated graft copolymerization of methacrylamide in natural rubber latex—I. The influence of non-rubber components

An investigation of the effect of non-rubber components on the persulphate initiated aqueous polymerisation of methacrylamide reveals that oxygen, ammonia and latex serum show retardation, no effect, and activation of the polymerization rate, respectively. The polymerization in the presence of sodium dodecyl sulphate is described by the rate expression $\text{R}{}_{\mathrm{P}}\text{= k[m][i]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[SdS]}{}^{\mathrm{?0.07}}$ which demonstrates that, unlike acrolein which is similarly water soluble, methacrylamide shows no tendency to undergo micellar polymerisation. Non-catalyzed polymerization was observed in the presence of rubber latex and attributed to initiation by rubber hydroperoxide groups.