J.U. Veenland

Proton magnetic resonance spectra of some 1,1-diarylalkenes

Abstract Compounds with general structure Ar 2 CC(CH 3 ) n H 2− n ( n =O, 1 or 2) have conformations which can be derived largely from NMR signals of protons and methyl groups at the double bond.

Proton magnetic resonance spectra of some methyl substituted N-methylbenzophenonimines and benzophenonimines

Abstract The configuration of benzophenonimines at −60°C and of N-methylbenzophenonimines at room temperature is determined by NMR spectrometry. Asymmetrically ortho -methyl substituted benzophenonimines are found to exist exclusively in a cis -configuration. The NMR spectra of protonated benzophenonimines and N-methylbenzophenonimines show the some feature as the NMR spectra of 1,1-diarylethylenes and 1,1-diarylpropenes.

Electronic and NMR spectra of some thienylphenyl-ketones and -thioketones

Abstract Steric effects manifest themselves more strongly in the electronic and NMR spectra of thienylphenylthioketones than in the spectra of the corresponding thienylphenylketones.

Electronic spectra of methyl substituted 1,1-diarylalkenes

Abstract The electronic spectra of 1,1-diarylpropenes are measured and interpreted in terms of phenyl-phenyl interaction and styrene conjugation within one molecule. Notwithstanding relatively small differences in absorption of the isomers, unambiguous conclusions with respect to configurations can be drawn. The configuration assignments on the basis of the electronic spectra are in agreement with those obtained from the NMR spectra.

Isomerzation of bromotolouenes under the influence of Al2Br6.HBr

Abstract The isomerization of the bromotoluenes in radioactive toluene with Al2Br6 as a catalyst was investigated. The isomerizations ortho-para and para-ortho are completely intermolecular, and are in agreement with the catalytic bromination mechanism given by Olah. The isomerization and formation of the meta-bromotolouene involve an intramolecular 1,2-shift.

Electron spin resonance of radical anions of alkyl substituted thienyl-phenyl ketones and related compounds

Abstract Radical anions of thienyl-phenyl ketones are studied by ESR spectrometry. Hyperfine splitting constants of the thienyl H-atoms are shown to depend on the conformation of the radical anion.

On the mechanism of the cyclization of ψ-ionone with deuterated acids☆

Abstract The cyclization of ψ-ionone with deuterated sulphuric acid and deuterated phosphoric acid to α- and β-ionone is discussed. β-ionone is formed predominantly via α-ionone.

The acid-catalysed reactions of ψ-ionone in water

Abstract In mixtures of sulphuric acid and water it is possible to hydrate ψ-ionone to a tertiary alcohol. Like ψ-ionone this “ψ-ionone hydrate” consists of two geometrical isomers—cis and trans—which are interconverted easily. A mechanism of this reaction is proposed. An analogous reaction of ψ-ionone with methanol is described; the product is a methoxyether with the same geometrical isomerism as the hydrate.

Nuclear magnetic resonance spectra of some protonated benzophenones

Abstract Protonated 2,2′-dimethylbenzophenone (in HSO 3 FSbF 5 ) shows at low temperature two methyl signals in the NMR spectrum. For some asymmetrically ortho -methyl substituted benzophenones two protonated isomers are found in HSO 3 FSbF 5 at sufficiently low temperatures (−60°C). The configuration of these isomers is established.

Cyclization of geraniolene and competitive cyclization-cyclialkylation of some phenyl derivatives

Abstract The cyclization of geraniolene ( 1 ; 2,6-dimethyl-1,5-heptadiene) to the isomeric cyclogeraniolenes ( 3, 4, 5 ) with aqueous sulphuric acid as a catalyst proceeds partly via 2,2,6,6-tetramethyltetrahydropyran ( 8 ). With phenyl- or benzyl-substituted geraniolenes a combined cyclization and intramolecular Friedel-Crafts alkylation (cyclialkylation) takes place. This leads to tricyclic systems containing cyclobutane and cyclopentane rings.