A theoretical study of the solid-state thermal isomerization reaction of methyl 4-(dimethylamino)benzenesulfonate in the energetic aspect

Theoretical Study on the Topochemical Nature in the Initiation Process of the Solid-State Thermal Isomerization Reaction of Methyl 4-(Dimethylamino)benzenesulfonate

“…In contrast, the methylsulfo group of MDBS in the crystal stands nearly vertical to the molecular long axis, so that it is directed to the dimethylamino group of the adjacent molecule, parallel to a molecular stacking axis along the b axis of the crystal (see Figure 1b). 6 Accordingly, in the crystal, the methylsulfo group in the cation intermediate may have a similar orientation with that of MDBS above. These structural characteristics could be related to the topochemical reactivity of the cation intermediate in the crystal.…”

“…In the case of the anion intermediate, the conformation of the dimethylamino group against the phenylene plane is different from that of MDBS. 6 Here we notice the inversion angle, which is defined as the angle between the plane fixed by the two C atoms and the N atom of the dimethylamino group and the N-C bond connecting the group with the phenylene ring, and also the twist angle, which is defined as the angle of rotation of the dimethylamino group around the N-C bond axis. The inversion and twist angles for the anion intermediate obtained to be 40.9°a nd 48.4°, respectively, are certainly different from 17.0°and 0.02°for the optimized MDBS, respectively, or 4.37°and 0.77°f or MDBS observed in the crystal, 11 respectively.…”

“…Here, our recent work has shown that the conformation of the methylsulfo group in the crystal is realized only in the crystal but not in the free space. 6 Although many studies on this solid-state reaction have been carried out so far, [6][7][8][9][10][11][12][13][14] the mechanism of this reaction still remains unsolved. Gavezzotti and Simonetta proposed possible ionic intermediates, shown in Figure 1c, in view of the unique crystal structure above.…”

“…That is, the molecular arrangement in the MDBS crystal is thought to be feasible for an S N 2 type reaction, since the methyl group of the methylsulfo group in an MDBS molecule is directed to the N atom of the adjacent molecule. Here, our recent work has shown that the conformation of the methylsulfo group in the crystal is realized only in the crystal but not in the free space 1 Schematics concerning solid-state thermal isomerization reaction from methyl 4-(dimethylamino)benzenesulfonate (MDBS) to N , N , N -trimethylbenzenaminium-4-sulfonate (TBS).…”

Thermal Solid-State Reaction of Methyl p-Dimethylaminobenzenesulfonate to p-Trimethylammoniumbenzenesulfonate Zwitterion: Optical Crystallographic Studies

“…Recent calculations showed that the internal energy of the isolated MSE molecule is much smaller than the one of the isolated ZWT molecule; but the authors found that the ZWT crystal is energetically more stable than the MSE crystal by about 71 kJ mol -1 . This value is slightly underestimated: the experimental enthalpy given by our isothermal calorimetric measurements is equal to −88 kJ mol -1 in the 300−360 K range .…”