CEQUINOR (CONICET-UNLP), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 962, 47 esq. 115, La Plata (B1900AJL), Buenos Aires, República Argentina.
J Phys Chem A. 2010 Mar 18;114(10):3703-12. doi: 10.1021/jp912044r.
Pure methoxycarbonylsulfenyl cyanide, CH(3)OC(O)SCN (I), and methoxycarbonylsulfenyl thiocyanate, CH(3)OC(O)SSCN (II), were prepared by reacting liquid CH(3)OC(O)SCl with either AgCN or AgSCN, respectively. Compounds I and II were characterized by (1)H NMR, CG-MS, and vibrational (FTIR and FT-Raman) techniques. The conformational properties have been studied by using vibrational spectroscopy [infrared (gaseous, liquid, and Ar matrix isolated), Raman (liquid) spectroscopy] together with quantum chemical calculations at the B3LYP and MP2 methods with the extended 6-311++G** and aug-cc-pVTZ basis sets. Compound I exhibits a conformational equilibrium at room temperature having the most stable form C(s) symmetry with a synperiplanar (syn) orientation of the carbonyl double bond (C=O) with respect to both the CH(3)O- and -SCN groups (syn-syn). Several bands assigned to a second conformer have been observed in the IR matrix spectra. This rotamer presents an antiperiplanar orientation of the thiocyanate group (syn-anti). Evaluating the equilibrium compositions at different temperatures by quenching the gas phase mixtures as Ar matrices allowed us to determine the conformational enthalpy difference DeltaH(0) = H(0)((syn-anti)) - H(0)((syn-syn)) = 0.80(18) kcal mol(-1). A similar conformational behavior has been determined for compound II. Thermodynamic properties were also computed at the high-level G2MP2 and G3 model chemistry methods. The importance of mesomeric (resonance) and anomeric (hyperconjugation) electronic interaction in the conformational behavior is evaluated by using the NBO approach for both species.
纯甲氧基羰基硫氰酸酯，CH(3)OC(O)SCN（I）和甲氧基羰基硫氰酸酯，CH(3)OC(O)SSCN（II），是通过分别将液体 CH(3)OC(O)SCl 与 AgCN 或 AgSCN 反应制备的。化合物 I 和 II 通过（1）H NMR、CG-MS 和振动（FTIR 和 FT-Raman）技术进行了表征。使用振动光谱[红外（气态、液态和 Ar 基质分离）、拉曼（液态）光谱]以及量子化学计算，在 B3LYP 和 MP2 方法下，使用扩展的 6-311++G**和 aug-cc-pVTZ 基组，研究了构象特性。化合物 I 在室温下表现出构象平衡，具有最稳定的 C(s)对称性形式，羰基双键（C=O）相对于 CH(3)O-和-SCN 基团呈顺式（syn）排列（syn-syn）。在红外基质光谱中观察到几个分配给第二种构象的谱带。这种旋转异构体呈现出硫氰酸根（syn-anti）的反式（anti）排列。通过将气相混合物淬火为 Ar 基质来评估不同温度下的平衡组成，使我们能够确定构象焓差 DeltaH(0) = H(0)((syn-anti)) - H(0)((syn-syn)) = 0.80(18) kcal mol(-1)。化合物 II 也表现出类似的构象行为。还在高级 G2MP2 和 G3 模型化学方法下计算了热力学性质。通过使用 NBO 方法对两种物质的离域（共振）和变旋（超共轭）电子相互作用的重要性进行了评估。
