Proton Magnetic Resonance Spectroscopy. Configurational Stability of Neohexyl(3,3-dimethylbutyl) Organometallic Compounds

The proton resonance spectra of dilute ether solutions of neohexyl(3,3-dimethylbutyl) organometallic compounds have been investigated as a function of temperature as a means of determining their configurational stabilities. Neohexyllithium, dineohexylmagnesium (free from magnesium chloride), and dineohexylzinc appear to undergo the inversion of configuration at the a-methylene groups at various temperatures. The activation energies for inversion are approximately 15, 20, and 26 kcal. for the lithium, magnesium, and zinc compounds, respectively. Inversion appears to be a first-order process for the lithium and magnesium compounds. This fact and the general dependence of the inversion rate on the nature of the metal suggest a dissociation-recombination mechanism (SE1). Trineohexylaluminum and dineohexylmercury were found to be configurationally stable up to 150-160º. The chemical shifts of the CH_2-CH_2 groupings in these organometallic compounds can be correlated with the electronegativity of the metal atoms

Études RMN en série hétérocyclique

Deux méthodes ont été utilisées pour essayer de déterminer la constante d’équilibre tautomère des pyrazoles non substitués à l’azote, à partir des déplacements chimiques 14N

Magnetic Resonance Spectroscopy. The Configurational Stability of Primary Grignard Reagents. 3,3-Dimethylbutylmagnesium Chloride

Detailed examination of the temperature dependence of the n.m.r. spectra of 3,3-dimethylbutylmagnesium chloride and bis(3,3-dimethylbutyl)magnesium indicates that inversion of configuration at the -CH_2Mg center occurs rapidly in ether solution at room temperature

A ^(15)N NMR Study of the Ring-Opening of Methylsydnonimine Hydrochloride

Nitrogen-15 NMR spectroscopy has been used to study the irreversible ring-cleavage or 3-methylsydnonimine hydrochloride samples separately labeled with ^(15)N at each or the three possible nitrogens. This reaction, which occurs in hydroxylic solvents on addition of base, initially yields principally the E and Z isomers or N-methyl-N-cyanomethylnitrosamine. While 3-methylsydnonimine itselr is surely a transient intermediate in the ring-opening, no measurable concentration of the free base could be detected by ^(15)N NMR. Hydrolysis or the cyano group of N-methyl-N-cyanomethylnitrosamine to give E and Z isomers of N-methyl-N-nitrosoglycine amide and N-methyl-N-nitrosoglycine could also be followed by ^(15)N NMR and is reasonably facile in that it occurs significantly at below room temperature