2-Methylpropane-l-thiol

Dried for several days with CaO, then distd from CaO. Purified as for 2-methylpropane-l-thiol. 

Methylpropane-l-thiol [513-44-0] M 90.2, b 41.2 /142mm, n s 1.43582, pKfist -10.8. Dissolved in EtOH, and added to 0.25M Pb(OAc)2 in 50% aqueous EtOH. The ppted lead mercaptide was filtered off, washed with a little EtOH, and impurities were removed from the molten salt by steam distn. After cooling, dilute HCl was added dropwise to the residue, and the mercaptan was distd directly from the flask. Water was separated from the distillate, and the mercaptan was dried (Na2C03) and distd under nitrogen. [Mathias J Am Chem Soc 72 1897 7950.]... 

Many applications of Kilpatrick and Pitzer s procedure for calculating thermodynamic properties of molecules with compound rotation have been reported. In all cases possible potential energy cross-terms between rotating tops have been neglected. Contributions from internal rotation of symmetric tops have been calculated using the appropriate tables." These tables have also been used in calculations for the internal rotation of asymmetric tops hindered by a simple -fold cosine potential. 3-Fold potential barriers have been assumed in calculations for the —OH rotations in propanol and 1-methylpropanol, the —SH rotations in propane-1-thiol, butane-2-thiol, 2-methylpropane-l-thiol, and 2-methylbutane-2-thiol, the C—S skeletal rotations in ethyl methyl sulphide, diethyl sulphide, isopropyl methyl sulphide, and t-butyl methyl sulphide, and the C—C skeletal rotations in 2,3-dimethylbutane, and 2-methylpropane-l-thiol. 2-Fold cosine potential barriers have been assumed in calculations in the S—S skeletal rotations in dimethyl disulphide and diethyl disulphide. ... 

A similar treatment of the torsion of other groups (e.g. of one methyl group in butane-2-thiol, both methyl groups in 2-methylpropane-l-thiol, and of the ethyl group in 2-methylbutane-2-thiol) as anharmonic oscillators has been adopted in recent work. ... 

Formation of a symmetrical sulphide (a) (e.g. dipropyl sulphide, Expt 5.204), is conveniently effected by boiling an alkyl halide (the source of carbocations) with sodium sulphide in ethanolic solution. Mixed sulphides (b) are prepared by alkylation of a thiolate salt (a mercaptide) with an alkyl halide (cf. Williamson s ether synthesis, Section 5.6.2, p. 583). In the case of an alkyl aryl sulphide (R-S Ar) where the aromatic ring contains activating nitro groups (see Section 6.5.3, p. 900), the aryl halide is used with the alkyl thiolate salt. The alternative alkylation of a substituted thiophenol is described in Section 8.3.4, p. 1160. The former procedure is illustrated by the preparation of isobutyl 2,4-dinitrophenyl sulphide (Expt 5.205) from l-chloro-2,4-dinitrobenzene and 2-methylpropane-1-thiol. 

A. Thallium(I) 2-methylpropane-2-thiolate. A 500-mL, round-bottomed flask equipped with a magnetie stirring bar and a pressure-equalizing dropping funnel to whieh a nitrogen inlet adapter is attached is charged with 47.2 g (0.189 mol) of thallium(l) ethoxide (Note 1) and 200 mL of anhydrous benzene (Note 2). Over a period of 15 min 19.2 g (24 mL, 0.213 mol) of 2-methylpropane-2-thiol (Note 1) is added. The... 

Scheme 82 Methylzinc complex with 2,2 -bis(camphorpyrazol-l-yl)-2-methylpropane-2-thiol.

Particularly important substances for the basic flavour of baked and cooked meat are aliphatic thiols (such as methanethiol), sulfides (such as dimethyldisulfide, dimethytrisulfide and dimethyltetra-sulfide), aldehydes (such as acetaldehyde, 2-methylpropanal and 3-methylbutanal), furans, pyridines and thiophenes with a mer-capto group in position C-3 and their corresponding disulfides and some other aliphatic and heterocyclic sulfur compounds. Examples of important aliphatic thiols are 3-mercaptobutan-2-one (8-179) and 3-mercaptopentan-2-one found in cooked beef. A mixture of 3-mercapto-2-methylpentane-l-ol diastereoisomers (Figure 8.86) has a broth-like, sweaty and leek-hke flavour. Very low odour threshold concentrations and an odour reminiscent of roasted meat are found in 2-methylfuran-3-thiol (8-180), which also occurs in beef broth, roasted coffee and other foods, 2,5-dimethylfuran-3-thiol, their corresponding disulfides and 2-furanmethanethiol (furfuryl mercaptan). The typical aroma of roast beef is found in... 

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