Rate and Product Studies of 5-Dimethylamino-Naphthalene-1-Sulfonyl Chloride under Solvolytic Conditions

Abstract

The solvolysis rate constants of 5-dimethylamino-naphthalene-1-sulfonyl chloride ((CH 3 ) 2 NC 10 H 6 SO 2 Cl, 1) in 31 different solvents are well correlated with the extended Grunwald-Winstein equation, using the N T solvent nucleophilicity scale and Y Cl solvent ionizing scale with sensitivity values of 0.96 ± 0.09 and 0.53 ± 0.03 for l and m, respectively; the correlation coefficient value was 0.955. These l and m values can be considered to support an S N 2 reaction pathway having a transition state (TS) structure similar to that of the benzenesulfonyl chloride reaction. This interpretation is further supported by the activation parameters, i.e., relatively small positive ΔH ≠ (12.0 to 15.9 kcal·mol) and large negative ΔS ≠ (−23.1 to −36.3 cal·mol) values, and the solvent kinetic isotope effects (SKIEs, 1.34 to 1.88). Also, the selectivity values (S = 1.2 to 2.9) obtained in binary solvents are consistent with the proposed mechanism.

Correlation of Rates of Solvolysis of Diphenylacetyl Chloride Using Extended Grunwald–Winstein Equation

“…As shown in Table , the l value of 0.76 is much smaller than those reported recently for the reactions proceeding through an A–E mechanism ( l = 1.5), but it is similar to those reported for bimolecular solvolyses of 9‐fluorenyl chloroformate(C 13 H 9 CH 2 OCOCl, l = 0.95), diphenylthiophosphinyl chloride((C 6 H 5 ) 2 PSCl, l = 1.00), 5‐dimethylamino‐naphthalene‐1‐sulfonyl chloride ((CH 3 ) 2 NC 10 H 6 SO 2 Cl, l = 0.96), 4‐methoxybenzenesulfonyl chloride(4‐CH 3 OC 6 H 5 SO 2 Cl, l = 1.07), and allyl chloroformate(CH 2 CHCH 2 OCOCl, l = 0.93). This result implies an S N 2 mechanism involving a nucleophilic attack at the carbonyl carbon atom of 1 by the solvent rather than an A–E mechanism.…”

“…The l / m values from the extended Grunwald–Winstein equation could be classified into two classes; l / m values of 1.2–3.5 for a bimolecular pathway; l / m values below 0.7 for an S N 1 pathway 3c,d . In these studies, the l / m value of 2.2 was obtained, and this gives a strong support for a bimolecular reaction mechanism in the solvolysis of 1 …”

Calculated Third Order Rate Constants for Interpreting the Mechanisms of Hydrolyses of Chloroformates, Carboxylic Acid Halides, Sulfonyl Chlorides and Phosphorochloridates

“…Although most sulfonyl chlorides react by the third order mechanism within the S N 3-S N 2 spectrum ( Section 2.2.4 ), there is evidence for a mechanistic changeover to the S N 2-S N 1 spectrum for electron-rich substrates; however, formation of sulfonyl cations is relatively unfavourable [ 21 ], and there is no evidence for an S N 1 mechanism. Evidence for the changeover will be based on KSIE data ( Table 4 , References [ 79 , 80 , 81 ]) and non-linear Equation (3) plots ( Figure 10 and Figure 11 ), but there is also support from independent evidence on alcohol/water selectivities [ 79 , 81 , 82 ].…”

“… a Data from Reference [ 13 ] at 25 °C; b Reference [ 79 ] at 35 °C; c Refers to 50/50 MeOH/water; d Reference [ 80 ] at 25 °C; e Reference [ 81 ] at 25 °C. …”

“… Plots of log k 3 vs. Y (Equation (3)) for solvolyses in acetone-water of 4-methoxybenzene sulfonyl ( 2 , Z = OMe) at 25 °C, and dansyl chlorides ( 16 ) at 35 °C; data from References [ 79 , 81 , 82 ]. …”