Alkyl and aryl derivatives of π-cyclopentadienyl compounds of chromium, molybdenum, tungsten, and iron

By using equilibrium thermodynamics, the sequence of condensation of mineral phases from a cooling nebula of solar composition has been calculated. The theoretical models suggest that the chemistry and mineralogy of Ca-Al-rich inclusions in C2 and C3 chondrites were established during condensation at temperatures above 1300 K. Fractionation of such inclusions is necessary to account for the refractory element depletions of ordinary and enstatite chondrites relative to the carbonaceous chondrites. The metal-silicate fractionation in ordinary chondrites took place in the nebula at a temperature below 1000 K and at .00001 atm total pressure. The volatile element depletion of C2 and C3 chondrites relative to C1 chondrites took place during chondrule formation: the most volatile elements are depleted in ordinary chondrites because they accreted before these elements were totally condensed.

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Early chemical history of the solar system

The present review offers an overview of nonclassical (e.g., with no pre- or in situ activation of a carboxylic acid partner) approaches for the construction of amide bonds. The review aims to comprehensively discuss relevant work, which was mainly done in the field in the last 20 years. Organization of the data follows a subdivision according to substrate classes: catalytic direct formation of amides from carboxylic and amines (section 2); the use of carboxylic acid surrogates (section 3); and the use of amine surrogates (section 4). The ligation strategies (NCL, Staudinger, KAHA, KATs, etc.) that could involve both carboxylic acid and amine surrogates are treated separately in section 5.

Nonclassical Routes for Amide Bond Formation

Conversion of Hydrogenic Materials to Hydrogen for Isotopic Analysis

The geochemistry of arsenic and its use as an indicator element in geochemical prospecting

Mass Spectra of Esters. Formation of Rearrangement Ions

Spectra and Structures of Cobalt Carbonyls1

Association of an acetylene with three metal atoms; new trinuclear cobalt complex. [Co atoms form 3-membered ring with 3 carbonyl groups bond to each Co atom]

The present invest,igat'ion deals with the reduction of organic compounds by the lit,hium-ethylenediamine system. Most st'udies with metal-ammonia and metal-amine syst'ems have been carried out using liquid ammonia. Although Kraus2 predicted in 1953 that methylamine, ethylamine, and ethylenediamine would be valuable solvents for studying the physico-chemical properties of solutions of metals in amines at higher temperatures, ethylenediamine has not hitherto been used in a metal-amine reducing system. The first use of the lower aliphatic amines for metal-amine reductions was recently reported by Benkeser et u Z . , ~ who showed that aromatic rings are reduced to monoolefins by lithiumethylamine. However, their attempt to replace ethylamine by higher primary amines gave poor yields, perhaps because lithium becomes progressively less soluble in these monofunctional amines as t'he ratio of nitrogen to carbon decreases. Since ethylenediamine contains one amine group per carbon at,om, and since its relatively high boiling point (117") is a potential advantage, we decided t'o investigate its use in a metal-amine system. Our results show that the lithium-ethylenediamine system, a t 90-loo", is a convenient and effective metal-amine combination for carrying out' reductioiis and cleavage react'ions of organic compound^.^

R.A. Friedel

Papers

Mass Spectra of Esters. Formation of Rearrangement Ions

Spectra and Structures of Cobalt Carbonyls1

Association of an acetylene with three metal atoms; new trinuclear cobalt complex. [Co atoms form 3-membered ring with 3 carbonyl groups bond to each Co atom]

Lithium in Ethylenediamine: A New Reducing System for Organic Compounds1

The Chemistry of Metal Carbonyls. III. The Reaction between Dicobalt Octacarbonyl and Dimethylamine1