Alison J. Green

Gauging the Donor Ability of the C-Si Bond. Results from Low-Temperature Structural Studies of gauche and Antiperiplanar β-Trimethylsilyl-cyclohexyl Esters and Ethers by Use of the Variable Oxygen Probe.

A plot of C–OR bond distance against pKa(ROH) for esters and ether derivatives of the antiperiplanar β-silyl alcohol (4) has a slope of –5.310–3. This represents a stronger response of the C–OR distance than was observed for the corresponding gauche β-silyl alcohol (5) and its derivatives. This result is consistent with the greater donor ability of a C–Si bond compared with a C–C bond. Comparison of these plots with those previously reported for derivatives (3) of tetrahydropyran-2-ol reveals that a C–Si bond is a weaker donor than an oxygen non-bonded pair of electrons. An estimate of the pKa value for 2,4-dinitrobenzenesulfenic acid (14) was derived from these plots.

Increasing our Impact

A 120% increase in Impact Factor, the introduction of XML publishing and CrossRef linking, and the launch of a new sister journal Environmental Chemistry were three of the highlights of 2004 for Australian Journal of Chemistry. The new Impact Factor for Australian Journal of Chemistry is 1.434—more than double the previous figure. Our citation ranking for journals in the category ‘chemistry, multidisciplinary’ has also risen—from 67th to 37th out of 122 journals. Moreover, among general chemistry journals, Australian Journal of Chemistry ranks 9th out of 54 (last year 21st; the top 20 are listed in Table 1). Almost all the chemistry journals in this table are journals of their local chemical societies, and the Impact Factor of Australian Journal of Chemistry has clearly been positively affected by the closer relationships we have developed with our local society, the Royal Australian Chemical Institute (RACI), and our regional community, through the Federation of Asian Chemical Societies (FACS). A glance at our nearest neighbours on Table 1 shows that we are now competitive with several other regional journals, such as Canadian Journal of Chemistry, Bulletin of the Chemical Society of Japan, Chemistry Letters, and Helvetica Chimica Acta. We will be working hard with authors, referees, and the Editorial Advisory Committee over the next few years to ensure that Australian Journal of Chemistry sits higher in this Table, among the regional journals of the UK, USA, and Germany (Chemical Communications, Journal of the American Chemical Society, and Angewandte Chemie and Chemistry – A European Journal, respectively).

cis- and trans-4-tert-Butylcyclohexyl p-Nitrobenzenesulfonate at 130K

The structures of the title axial and equatorial cyclohexyl p-nitrobenzenesulfonate esters, C 16 H 23 NO 5 S, determined at 130 K are reported. The C alkyl -O ester bond distances of 1.487(2) and 1.492(2)A are not significantly different from one another. The geometry of the sulfonate function with respect to both the phenyl and cyclohexane rings is essentially identical in both structures.

endo-3-Trimethylsilyl-2-norbornyl 2-Nitrobenzenesulfinate

The structure of the title compound, C16H23NO4SSi, was determined in order to determine the C(alkyl)—O(ester) bond distance for comparison purposes. There exists a close contact [O3⋯S 2.766 (2) A] between one of the nitro O atoms and the sulfinate S atom. The C-O bond distance is 1.464 (3) A.

trans-4-tert-Butylcyclohexyl 2,4-Dinitrobenzenesulfenate

The low-temperature structure of trans-4-tert-butylcyclohexyl 2,4-dinitrobenzenesulfenate, C 16 H 22 N 2 O 5 S, is reported. The C-O bond distance is 1.473 (2) A. A close contact exists between a 2-nitro O atom and the sulfenate S atom which is evidence for a significant interaction between these two; the pattern of bond distances in the aromatic ring and the nitro groups is consistent with this.

endo-2-Norborneol 2,4-Dinitrobenzoate

The structure of the title compound, C 14 H 14 N 2 O 6 (endobicyclo[2.2.1]heptan-2-yl 2,4-dinitrobenzoate), was determined at 130 K to obtain an accurate measurement of the C-O bond length for comparison purposes. Steric interactions between the carboxyl function and the 2-nitro group of the ester result in these two groups twisting out of the plane of the aromatic ring. The C(alkyl)-O bond length is 1.465 (2)A.

Rearrangement of r-5-methyl-c-2-(trimethylsilyl)cyclohexan-t-yl 2,4-dinitrobenzoate in chloroform

Isomerisation of the title compound 3 to the ester 4 in deuteriochloroform is believed to occur via rearrangement of an intermediate β-trimethylsilyl substituted carbocation, with subsequent capture by the 2,4-dinitrobenzoate anion.