- Structure-odor correlations in homologous series of alkanethiols and attempts to predict odor thresholds by 3d-qsar studies
-
Homologous series of alkane-1-thiols, alkane-2-thiols, alkane-3-thiols, 2-methylalkane-1-thiols, 2-methylalkane-3-thiols, 2-methylalkane-2-thiols, and alkane-1,??-dithiols were synthesized to study the influence of structural changes on odor qualities and odor thresholds. In particular, the odor thresholds were strongly influenced by steric effects: In all homologous series a minimum was observed for thiols with five to seven carbon atoms, whereas increasing the chain length led to an exponential increase in the odor threshold. Tertiary alkanethiols revealed clearly lower odor thresholds than found for primary or secondary thiols, whereas neither a second mercapto group in the molecule nor an additional methyl substitution lowered the threshold. To investigate the impact of the SH group, odor thresholds and odor qualities of thiols were compared to those of the corresponding alcohols and (methylthio)alkanes. Replacement of the SH group by an OH group as well as S-methylation of the thiols significantly increased the odor thresholds. By using comparative molecular field analysis, a 3D quantitative structure-activity relationship model was created, which was able to simulate the odor thresholds of alkanethiols in good agreement with the experimental results. NMR and mass spectrometric data for 46 sulfur-containing compounds are additionally supplied.
- Polster, Johannes,Schieberle, Peter
-
p. 1419 - 1432
(2015/03/05)
-
- Method of making 2-thiols
-
A process for selectively making 2-thiols from alpha olefins is described. The process includes contacting a linear or branched alpha olefin having with H2S in the presence of a catalyst and recovering the 2-thiol from a product mixture. The catalyst includes a support and at least one metal selected from Group IIIA-VIIIA and the branched olefin is branched at the 3-position or higher with respect to the olefin double bond. Compositions wherein the 2-thiols are substantially free of 1 -thiol and 3-thiol isomers are also described.
- -
-
Page/Page column 5
(2008/06/13)
-
- Mechanisms of the hydrodenitrogenation of alkylamines with secondary and tertiary α-carbon atoms on sulfided NiMo/Al2O3
-
The HDN of alkylamines with secondary and tertiary α-carbon atoms (2-pentylamine, 3-methyl-2-butylamine, 3,3-dimethyl-2-butylamine, 2-methylcyclohexylamine, 2-methyl-2-butylamine) and benzylamine and the HDS of corresponding alkanethiols were studied over sulfided NiMo/Al2O3. Alkanethiols and dialkylamines were primary products in the HDS of the amines with secondary products, formed from elimination and hydrogenolysis of the alkanethiols, as confirmed by the similar alkenes/alkane ratios in the HDN of the alkylamines and HDS of the corresponding alkanethiols. 2-Methyl-2-butylamine and benzylamine reacted much faster than the amines with secondary α-carbon atoms. Methylbutenes and methylbutane were the primary products of 2-methyl-2-butylamine, and toluene was the primary product of benzylamine. This and the different methylbutenes/methylbutane ratios in the HDS of 2-methyl-2-butylamine and HDS of 2-methyl-2-butanethiol indicated that 2-methyl-2-butylamine, with a tertiary α-carbon atom, and the activated benzylamine reacted by means of an E1 mechanism. The substitution of the NH2 group by H2S led to an alkanethiol and NH3 and, thus, to total denitrogenation. Substitution by an amine led to a dialkylamine and NH3 and to 50% nitrogen removal. High partial pressures of H2S and alkylamine increased the rate of transformation of alkylamine to alkanethiol and thus, of denitrogenation. However, the rate of sulfur removal from the alkanethiol decreased.
- Zhao,Prins
-
p. 532 - 544
(2007/10/03)
-
