The attachment of a marine Pseudomonas sp. to a variety of surfaces was investigated, and the number of bacteria which became attached was related to the surface charge and degree of hydrophobicity of the substratum. Large numbers of bacteria attached to hydrophobic plastics with little or no surface charge [Teflon, polyethylene, polystyrene, poly(ethylene terephthalate)]; moderate numbers attached to hydrophilic metals with a positive (platinum) or neutral (germanium) surface charge; and very few attached to hydrophilic, negatively charged substrata (glass, mica, oxidized plastics). The results suggest that both electrostatic and hydrophobic interactions are involved in bacterial attachment.

Influence of Substratum Characteristics on the Attachment of a Marine Pseudomonad to Solid Surfaces

Alpha-fluorinated ethers, thioethers, and amines: anomerically biased species.

Hydrozirconation has recently been developed as a procedure for functionalizing alkenes, alkynes, and 1,3-dienes via organozirconium(IV) intermediates. These intermediates react with a variety of electrophilic reagents to give organic products in high yield. Mechanisms of reactions involved in these sequences are discussed.

Hydrozirconation: A New Transition Metal Reagent for Organic Synthesis

The distant and selective activation of unreactive C–H and C–C bonds remains one of the biggest challenges in organic chemistry. In recent years, the development of remote functionalization has received growing interest as it allows for the activation of rather challenging C–H and C–C bonds distant from the initiation point by means of a “metal-walk”. A “metal-walk” or “chain-walk” is defined by an iterative series of consecutive 1,2- or 1,3-hydride shifts of a metal complex along a single hydrocarbon chain. With this approach, simple building blocks or mixtures thereof can be transformed into complex scaffolds in a convergent and unified strategy. A variety of catalytic systems have been developed and refined over the past decade ranging from late-transition-metal complexes to more sustainable iron- and cobalt-based systems. As the possibilities of this field are slowly unfolding, this area of research will contribute considerably to provide solutions to yet unmet synthetic challenges.

Walking Metals for Remote Functionalization.

Recent Advances in Hydrometallation of Alkenes and Alkynes via the First Row Transition Metal Catalysis

An improved process is disclosed for preparing polyphenylene ethers in which a complexing agent selected from the group consisting of biguanide, di-o-tolylbiguanide, dicyanodiamide, and L-Arginine is employed to terminate the oxidative coupling reaction and facilitate the recovery of the polymer.

Method for preparing polyphenylene ethers

Titanium-Catalyzed Rearrangement and Olefin-Exchange of Grignard Reagents1

Synthetic Applications of the Titanium-Catalyzed Exchange of Olefins with Grignard Reagents1a

Films of low-density polyethylene which were exposed to a corona discharge in oxygen at a pressure of 1 atm. lost weight and decreased in thickness due to oxidation of the surface to volatile products (principally carbon dioxide and water). The weight loss was directly proportional to the time of exposure and was independent of film thickness. The infrared spectra of the films after exposure to the discharge showed a strong band at 1717 cm.–1 due to carbonyl groups. After a short time in the discharge, the formation of new carbonyl groups in the polymer was balanced by their destruction by oxidation to volatile products at the surface. The intensity of the carbonyl band initially increased rapidly with increasing exposure, but reached a maximum value after 4 hr. and then showed no further change for 90 hr., during which time the thickness of a film originally 4 mils thick was reduced to approximately 1 mil. The data indicate that the carbonyl groups are present in a relatively thin oxidized layer, estimated to be between 5 X 102 and 7 X 104 A. in depth. Carbonyl groups were also formed in films which were not in the discharge area but were exposed to the ozone produced by the discharge. The position of the carbonyl band in both types of oxidized film is consistent with either carboxylic acids or ketone. The relative amounts of the two were determined by soaking the films in ethanolic sodium hydroxide solution to convert the acid to carboxylate ion and measuring the decrease in intensity of the 1717-cm.–1 band. In the sample which was exposed to the discharge, 60% of the carbonyl was carboxylic acid and 40% was ketone. In the sample exposed only to ozone, the proportion was 30% acid and 70% ketone. It is believed that the carbonyl groups in both cases are the result of attack of ozone on the carbon-carbon double bonds of the polymer. Small amounts of oxalic acid and other low molecular weight acids were also produced in films exposed to the discharge, presumably due to oxidation of the surface by one or more of the unstable species of the corona.

Glenn D. Cooper

Papers

Method for preparing polyphenylene ethers

Titanium-Catalyzed Rearrangement and Olefin-Exchange of Grignard Reagents1

Synthetic Applications of the Titanium-Catalyzed Exchange of Olefins with Grignard Reagents1a

The action of oxygen corona and of ozone on polyethylene

Cleavage and Disproportionation of Polychlorodisilanes, Trichloromethylchlorosilanes and Hexachlorodisiloxane by Amines and Ammonium Salts