Dimethyl Isomers Research Articles

Conversion of linoleic and latex furanoid acid to fish C18 dimethyl furanoid isomers

Methyl 9(10), 12(13)-dioxo-octadecanoate (derived from methyl linoleate) and 10, 13-dioxo-11-methyl-octadecanoate (derived from the latex of the rubber plant) were methylated at the methylene carbons located between the two oxo-groups (using Mel, KOH in DMSO) and cyclodehydration furnished a mixture of methyl 9(10),-12(13)-epoxy-10(11), 11(12)-dimethyloctadeca-9(10), 11(12)-dienoates and methyl 10, 13-epoxy-11, 12-dimethyloctadeca-10, 12-dienoate respectively.

Azimine. I. Bildung und Stereoisomerie von 2, 3‐Diaryl‐ und 2, 3‐Dialkyl‐1‐phthalimido‐aziminen

Azimines. I. Synthesis and Stereoisomerism of 2, 3‐Diaryl‐ and 2, 3‐Dialkyl‐1‐phthalimido‐aziminesTeilweise vorgetragen in der Versammlung der Schweizerischen Chemischen Gesellschaft in Lausanne am 7./8. Mai 1971 und als Autoreferat veröffentlicht [1]. Special examples of a new class of compounds, the open‐chain azimines (1), have been prepared and their properties examined.Addition of phthalimido‐nitrene (4), generated by lead tetraacetate oxidation of N‐aminophthalimide (3), to cis‐ and trans‐azobenzene (6 and 5), ‐azo‐p‐toluene (8 and 7), and to trans‐azomethane (9), ‐azoethane (10) and ‐azo‐α‐phenylethane (11) afforded the separable cis‐ and trans‐isomers of 2, 3‐diphenyl‐ (12 and 13), 2, 3‐di‐p‐toyl‐ (14 and 15), 2, 3‐dimethyl‐ (16 and 17), 2, 3‐diethyl‐ (18 and 19) and 2, 3‐di‐(α‐phenylethyl)‐1‐phthalimido‐azimines (20 and 21) in different ratios (see Scheme 1).The constitution of the nitrene azo compound adducts as azimines was derived from their properties, especially from the conjugation effect (visible in the UV. spectra) of the aryl‐substituted compounds and from the non‐equivalence (shown by the 1H‐NMR. spectra) of the substituents on the two nitrogen atoms derived from the azo compounds. This evidence excluded the triaziridine 22 and an alternative azimine constitution 23 for the adducts.Of the two stereoisomers obtained for each of the azimines, the aryl‐substituted examples 12/13 and 14/15 were readily interconverted by warming in solution, the cis‐isomers 12 and 14 exceeding the trans‐isomers 13 and 15 in the equilibrium. The dialkyl‐azimines appear to be configurationally more stable, since interconversion of the dimethyl‐azimines 16 and 17 was not possible under the same conditions, and also not before another thermal reaction took place (see below).The identification of the N(2)‐N(3) bond as the stereogenic center, i.e. that the stereoisomerism of the azimines is due to the difference in relative position at N(2) and N(3) of the substituents derived from the azo compounds, as well as a configurational assignment was possible in the aryl‐substituted examples on the basis of the UV. spectroscopic comparison of the isomeric azimines with the corresponding stereoisomeric azoxy compounds: The cis‐azimines 12 and 14 showed absorptions similar to those of cis‐azoxybenzene and cis‐azoxy‐p‐toluene, and the trans‐azimines 13 and 15 showed absorptions similar to those of the respective trans‐azoxy compounds. With respect to the configuration of the alkyl‐substituted azimines, it was observed that the isomers 17 and 19, which from their formation and chromatographic behaviour are likely to be the trans‐isomers, show a visible coupling (∽ 1 Hz) between the two H (α)'s in the 1H‐NMR. spectrum, whereas the dimethyl isomer 16 (cis) does not exhibit such a coupling.Thermal treatment of four azimines, namely 12, 14, 16 and 17, in solution for a longer time afforded the corresponding N, N′‐disubstituted N, N′‐phthaloyl‐hydrazines 27, 28 and 29. The order of velocity of this fragmentation with nitrogen extrusion was 12/13 ≈︁ 14/15 > 16(cis) > 17(trans).

Photoelectron spectra of 1,2,4-triazine and some methyl derivatives

The He(I) photoelectron (PE) spectra of 1,2,4-triazine, its three monomethyl isomers, two dimethyl isomers, and trimethyl-1,2,4-triazine are reported. The spectra are interpreted by comparison with the results of MO calculations and empirical correlation procedures.

Nuclear magnetic resonance spectra of o-hydroxythiobenzamides: the intramolecular hydrogen bond as a conformational probe

The OH and NCH2 proton signals of 1-(2′-hydroxythiobenzoyl)-2-methylpiperidine (2) are resolved into separate peaks assigned to four conformers (EA, EB, ZA, and ZB) in 220 MHz nmr spectra at −50 °C. All have a strong intramolecular [Formula: see text] hydrogen bond. The ZB and EB conformers have the lowest and highest ground state energies, respectively. Exchanges between A and B conformers have a higher energy barrier than exchanges between Z and E isomers, but by +40 °C all four conformers interchange rapidly. The nature of all possible interchange processes is considered and a potential energy surface with respect to rotation about the Ph—C(S) and C—N bonds is presented. For the 4-methyl analogue of 2 low temperature nmr spectra exhibit two sharp OH signals arising from A and B conformers. For 2,6-di-methyl-4-(2′-hydroxythiobenzoyl)morpholine the A/B OH doublet of the cis dimethyl isomer can be distinguished from that of the trans isomer. Thus it is demonstrated that the intra-molecularly hydrogen bonded OH proton is a good spectroscopic conformational probe. Nuclear magnetic resonance, ir, and uv data all indicate that in the 2,6-dimethylpiperidine analogue of 2 the CNC and Ph—C(S)N planes are perpendicular due to steric interference. Coplanarity of the phenyl ring with the thioamide group is attributed to a very strong intramolecular [Formula: see text] hydrogen bond, in equilibrium with a proton transferred [Formula: see text] form in solution. This structure resembles the transition state for rotation in the most readily achieved exchange between conformers of 2.

Etude biochimique de la secretion des glandes tergales des blattaria

The chemical composition of the tergal gland secretion was investigated in five species of cockroaches Blattella germanica, Supella supellectilium, Leucophaea maderae, Nauphoeta cinnerea, and Periplaneta americana). In all species the secretion is a mixture of proteins and volatile products. In Blaberoidea (four species) the tergal glands are present only in adult males and play a part during mating. We find four to eight proteins (several are glycoproteins) and 10 volatile products: myristic, palmitic, and oleic acids; benzothiazol, two isomers of nonylphenol, two isomers of hydroxybenzylic alcohol, dimethyl and trimethyl-naphthalene. Their percentages vary according to the species. In P. americana the tergal glands are present in adults of both sexes and in all larvae. Proteins are more numerous in larvae (6) than in adults (3) Several are glycoproteins. One of these proteins has a mol. wt of 10300. Two of the glycoproteins have been isolated, their mol. wt are 5600 and 6800. In adult females we find 6 volatile products: 2 and 3 pentanone, 3 octanone, and 3 isomers of methyl cyclohexanone. In adult males only 3: 2 and 3 pentanone, 3 octanone and in larvae only 2 and 3 pentanone. The function of all these products is discussed.

Applications of gas-liquid chromatography to the determination of polysaccharide structures : Model studies on a synthetic D-galactan

When a complex polysaccharide is degraded by the Smith procedure, mixtures of O- i-glycosylalditols are produced which are difficult to separate by conventional methods. Some O- d-galactosylalditols, obtained by degradation of a synthetic d-galactan, have been separated as their trimethylsilyl derivatives by gas-liquid chromatography and the following have been characterized: i- O-(α- d-galactopyranosyl)-glycerol and the β- d anomer; 2- O-(α- d-galactopyranosyl)- d-threitol and the β- d anomer; i- O-(α- d-galactopyranosyl)- d-threitol and the β- d anomer. The α- D-anomers had shorter retention times than the β- d anomers and they were differentiated by their reaction with β-galactosidase. In addition, i- O-( l-arabinofuranosyl)glycerol was isolated by paper chromatography. Hydrolysis of the fully methylated d-galactan gave a large number of methylated sugars of which the monomethyl and some of the dimethyl isomers were identified by a combination of periodate degradation and gas-liquid chromatography. The d-galactan was shown to contain both furanose and pyranose residues, and to be highly branched, with approximately 25% of the end-groups furanose.