C 9 H 9 NO 2 S, orthorhombic, Pna2 1 (no. 33), a =9.6168(2) Å, b =9.0206(2) Å, c =11.0006(2) Å, V =954.3 Å 3 , Z =4, R gt (F) =0.0242, wR ref (F 2 ) =0.0659, T =200 K.
Source of materialThetitle compound was obtained upon reacting benzoyl chloride with ammonium thiocyanate in acetone and, subsequently, with boiling methanol. Crystals suitable for the Xray analysis were obtained upon storage of the oily residue at room temperature for one week.
Experimental detailsCarbon-bound Hatoms were placed in calculated positions (C-H 0.95 Åfor aromatic carbon atoms) and were included in the refinement in the riding model approximation, with U iso (H) setto 1.2U eq (C). The Hatoms of the methyl group were allowed to rotate with afixed angle around the C-C bond to best fit the experimentalelectron density (HFIX 137 in the SHELX program suite [5]), with U iso (H) setto1.5U eq (C). The nitrogen-bound Hatom was placed in ac alculated position (N-H 0.88 Å) and was included in the refinement in the riding model approximation, with U iso (H) setto1.2U eq (N).
DiscussionChelating ligands have found widespread use in coordination chemistry. Coordination compounds formedb yt hem show a markedly higher stability than coordination compounds formed from comparable but exclusively monodentate ligand systems. (8) Å. This finding can be rationalized by assuming amide-type resonance spanning the sidechain. However, the aromatic system does not seem to take part in this resonance as the least-squares planedefinedbyits carbon atomsintersects at an angleof28.18(5)°with thel east-squares planej ustd escribed.T he length of theC -S bond,however, is notsupportiveofinvolving thelatterinresonanceasits valueof1.6253(12) Åissignificantly below the most commonvalues reported for molecular structures featuring comparableO-(C=S)-N moieties in the CambridgeStructural Database [2].I nt he crystal, C-H×××Oc ontacts whose range falls by more than 0
A reaction of an acid chloride with a diamine yielded a diamide. m-Toluic acid was chlorinated to m-toluoyl chloride and subsequently reacted with 4-methyl-o-phenylenediamine in pyridine to obtain 3-methyl-N-[2-(3-methylbenzamido)phenylbenzamide (I). 2-(3-Methylphenyl)-1H-benzimidazole (II) has been obtained upon reacting o-phenylenediamine with m-toluic acid in polyphosphoric acid and toluene. The compounds have been characterized by IR, NMR, microanalyses and GC-MS. The crystal structures of the compounds have been discussed. DFT calculations of the frontier orbitals of the precursor compounds have been carried out to ascertain the groups that contribute to the HOMO and LUMO, and to study their contribution to the reactivity in the formation of the diamides and benzimidazoles. The synthesis of the amide from a diamine was seen to be favoured in the presence of a good leaving group attached to the carbonyl as in the case of acid chloride. However, the synthesis of benzimidazoles was found to be favoured in the presence of an excess of a protonating agent and high temperature.
A base-catalyzed conversion of aldehydes to benzimidazoles has been achieved. The compounds have been characterized by IR, NMR, micoranalysis, and GC-MS. The reaction for the formation of benzimidazoles has been monitored with 1 H NMR and IR. The crystal structures of two derivatives, 2-(2chlorophenyl)-1H-benzimidazole and 2-(1H-benzimidazol-2-yl)-4-nitrophenol, are presented. A study of the DPPH scavenging activity of these compounds showed that 2-(1H-benzimidazol-2-yl)phenol (2), 2-p-tolyl-1Hbenzimidazole (3) and 2-(4-methoxyphenyl)-1H-benzimidazole (7) gave IC50 values 1974, 773 and 800 µM.
The reaction mechanism for the formation of N-(carbomylcarbamothioyl)benzamide has been successfully computed with the B3LYP/6-31g(d) functional and basis set and compared with 1H NMR monitoring of the progress of the reaction with time. The reaction is proposed to proceed through two transition states: Ts1 (the rate-determining step) with highly unstable species (with a requisite orientation for the reaction to proceed), and Ts2 with a lower energy leading to the product. Computation of the reaction pathway was also carried out using the B3PW91/6-31G(d), M06/6-31G(d) and Wb97XD/6- 31G(d) functionals and basis set. These results do not present a clear reaction pathway compared to that given by the B3LYP/6-31G(d).
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