Frederick R. Jensen

Stereochemistry of the photochemical and thermal insertion of oxygen into the carbon—cobalt bond of alkyl(pyridine)cobaloximes

Abstract The insertion of molecular oxygen into the carbon—cobalt bond of optically active alkyl(pyridine)cobaloximes proceeds with complete loss of configuration at the asymmetric carbon center.

Relative enantiomer binding and reaction rates with propanediol dehydrase

In the dioldehydrase reaction, L(+) propanediol reacts at a faster rate than the D(−)-isomer in competitive reactions, but when the diols are run independently the rate of the D(−)-isomer is 2.3 times greater than that of the L(+)-isomer. It is assumed that this reversal is due to a difference in the Michaelis-Menten constants. A ratio of KmD(−)/KmL(+) = 3.2 ± 0.3 at 25° is calculated from a series of competitive reactions. It is concluded that the binding site is such that while both isomers are accomodated readily, the D(−)-isomer is hindered to some degree in its approach to the binding site. However, once the enzyme-substrate complex is formed, the D(−)-isomer is in a more favorable configuration for further reaction.

A Simple, Effective Device for Supplying a Controlled Temperature Gas Stream

A very simple but highly effective system for supplying a gas stream at a temperature variable from room temperature to the temperature of the heat exchanger bath is reported.

A Modification of the Varian HR‐60 NMR Spectrometer Probe for Operation at Very Low Temperatures

An insert design and probe modification is given which makes it possible to obtain spectra with good spinning and resolution as conveniently at −170°, or below, as can be obtained at 0°. Because of the placement of the pickup coil, the resolution and sensitivity are superior to commercial inserts. At −170° the temperature variation through the sample region is no more than ±0.01°.

Preparation of 1-methyl-2,2-diphenylcyclopropylcobaloxime and theoretical considerations for its mode of formation

The title compound, which contains a stable tertiary alkylcobalt σ-bond, is readily obtained from the reaction of pyridine[bis(dimethylglyoximato)]cobalt(I) and 1-methyl-2,2-diphenylcyclopyl bromide; five mechanisms for the reactions of low-valent metal ions and alkyl halides are discussed.