N-(2-Methylphenylsulfonyl)propanamide

In the title compound, C10H13NO3S, the conformations of the N—H and C=O bonds of the SO2—NH—CO—C segment are anti to each other, while the amide H atom is syn with respect to the ortho-methyl group in the benzene ring. The C—S—N—C torsion angle is −66.7 (2)°. The crystal structure features inversion-related dimers linked by pairs of N—H⋯O(S) hydrogen bonds.


Comment
The hydrogen bonding preferences of sulfonamides has been investigated (Adsmond & Grant, 2001). The nature and position of substituents play a significant role on the crystal structures and other aspects of N-(aryl)-amides and N-(aryl)-sulfonamides (Gowda et al., 2003(Gowda et al., , 2004Shakuntala et al., 2011a,b). As a part of studying the effects of substituents on the structures of this class of compounds, the structure of N-(2-methylphenylsulfonyl)-2-methylacetamide (I) has been determined ( Fig. 1). The conformations of the N-H and C=O bonds of this segment in the structure are anti to each other, similar to that observed in N-(2-methylphenylsulfonyl)-acetamide (II) (Shakuntala et al., 2011b) and N-(2-methylphenylsulfonyl)-2,2,2trimethylacetamide (III) (Shakuntala et al., 2011a). Further, the conformation of the amide H atom is syn to the ortho-methyl group in the benzene ring, similar to that observed between the amide H atom and the ortho-methyl group in (II) and (III).
The molecules in (I) are bent at the S-atom with a C-S-N-C torsion angle of -66.7 (2)°, compared to the values of -58.2 (2)° in (II) and -65.4 (2)° in (III).
In the crystal structure, the pairs of intermolecular N-H···O hydrogen bonds (Table 1) link the molecules through inversion-related dimers into chains running in the direction of b-axis. Part of the crystal structure is shown in Fig. 2.

Experimental
The title compound was prepared by refluxing 2-methylbenzenesulfonamide (0.10 mole) with an excess of propanoyl chloride (0.20 mole) for one hour on a water bath. The reaction mixture was cooled and poured into ice cold water. The resulting solid was separated, washed thoroughly with water and dissolved in warm dilute sodium hydrogen carbonate solution.
The title compound was reprecipitated by acidifying the filtered solution with glacial acetic acid. It was filtered, dried and recrystallized from ethanol. The purity of the compound was checked by determining its melting point. It was further characterized by recording its infrared spectra.
Prism like colourless single crystals of the title compound used in X-ray diffraction studies were obtained from a slow evaporation of an ethanolic solution of the compound.

Refinement
The H atom of the NH group was located in a difference map and later restrained to the distance N-H = 0.86 (2) Å. The other H atoms were positioned with idealized geometry using a riding model with the aromatic C-H distance = 0.93 Å, methyl C-H = 0.96 Å, methylene C-H = 0.97 Å. All H atoms were refined with isotropic displacement parameters (set to 1.2 times of the U eq of the parent atom).   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.