THE SULPHUR GROUP

Solid acids can also be prepared from these materials by transformation of the sulphur group to the sulphonic acid, very closely related to sulphuric acid, one of the most commonly used acids industrially. The material can be easily recovered and easily handled since the acidity resides within pores, it cannot come into contact with living tissue. Important transformations, such as the formation of synthetic lubricants and intermediates for fragrances, have already been reported using these materials. The scope for such materials in future is enormous. 

In the halide group the most active lone pair is found in the phosphortrihalides. The stability of the boron complexes AXZ.BXZ decreases in the sequence PXj -> AsXz SbX3, no antimony compounds being observed. The halides of the sulphur group do not form compounds at all it seems improbable that the only reason for this behaviour is the disproportionation of these halides. 

This exceptional behaviour of the tellurates is one of the arguments used by those chemists who wish to place tellurium elsewhere than in the sulphur group of elements. 

The substance, which is of a type general to the sulphur group (see pp. 6, 338), is a red solid which softens at 30° C. without melting. It is decomposed by water mainly into tellurium and sulphuric acid, whilst in solution in sulphuric acid it undergoes oxidation into basic tellurium sulphate on warming. Between 35° and 90° C. it is stated that the red compound is converted into an isomeric form having a reddish-brown colour.7 (See also p. 379.)... 

Chemical alteration of proteins under heating is particularly important at basic pH values this has been shown for -SH and S-S groups by Watanabe and Klostermeyer in the paper already cited [143], but it is probably not limited to these groups. The net charge of BLG is about the same at pH 9 and at pH 2 however, in 0.01 M NaCl, q was observed to be zero at pH 9 against 75% at pH2 under the same conditions [28] the difference is probably related to modification of the sulphur groups of the protein at alkaline pH. 

The sulphur group comprises sulphur, selenium, tellurium and polonium. Although polonium belongs chemically to this group it is convenient to discuss it later along with the radio-elements (p. 311). 

An alternative to the bis-lactim ether approach is based on condensations of saturated five-membered heterocycles such as imidazolidinone (532) which can now be obtained in an optically pure state by a straightforward classical resolution/ The related oxazolidinone (533) has been obtained from methionine and used to prepare (R)-amino-acids [cf. (528) ] as well as the vinyl substituted derivatives(534) by oxidation and elimination of the sulphur group." Yet more general routes to chiral amino—acids have been reported using a variety of asymmetrically substituted ester enolate equivalents (535) in combination with the electrophilic nitrogen source di-t-butyl... 

An alternative method to halolactonization of unsaturated acids consists of reaction with triethylamine followed by benzenesulphenyl chloride to give phenyl-thio-lactones (e.g. 42). Elimination of the sulphur group by standard methods gives saturated or unsaturated fused lactones. Essentially the same method, but using phenylselenenyl chloride, has also been reported. Vinyloxirans undergo carbonyl insertion when treated with iron pentacarbonyl oxidation of the resulting complexes (e.g. 43) with cerium(iv) gives (44) as the only lactone isolated. ... 

The first publication about Crookes discovery appeared in Chemical News on March 30, 1861, under the title On the Existence of a New Element Probably from the Sulphur Group . Here the author was wrong since, as we know, thallium has nothing in common either with sulphur or with its analogues. A year later Crookes recognized his mistake and published another paper titled Thallium, a New Chemical Element where no analogy with sulphur was drawn. 

Crookes W (1861) On the existence of a new element, probably of the sulphur group. Chem News 3 193-194... 

Figure 7.1 Volt-equivalent versus oxidation number for the sulphur group.

It will be seen that the oxygen group is chosen for suffix in example (d), but the sulphur group in example (e). This is because esters rank for priority immediately after their respective acids, so that for (d) carboxylate and not sulphonate is the principal functional group, and this is not altered because the systematic naphthalenecarboxylate is abbreviated to naphthoate however, ether and sulphide groups both rank after alcohols, phenols, and thiols— the rule in fact has considerable empiricism in its make-up. 

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