Department of Chemistry, Kent State University, Kent, Ohio, 44242, USA.
Phys Chem Chem Phys. 2010 Aug 1;12(29):8350-6. doi: 10.1039/c001705a. Epub 2010 May 26.
Rotational spectra of p-, m-, and o-cyanophenol have been measured in the range of 10.5-21 GHz and fit using Watson's A-reduction Hamiltonian coupled with nuclear quadrupole coupling interaction terms for the (14)N nuclei. Ab initio calculations at the MP2/6-311++G(d,p) and CCSD(T)/6-311++G(d,p) levels predict the cis conformers of m- and o-cyanophenol to be more stable than the corresponding trans conformers. A natural bond orbital analysis of the hydrogen bonding interaction in o- and m-cyanophenol revealed an intramolecular hydrogen bond that preferentially stabilizes the cis conformer of o-cyanophenol but there was no evidence of hydrogen bonding interactions in cis m-cyanophenol. We recorded 25 a- and b-type rotational transitions for cis o-cyanophenol; the rotational constants are A = 3053.758(2) MHz, B = 1511.2760(3) MHz, and C = 1010.7989(2) MHz. The trans conformer of o-cyanophenol was not observed. We recorded 14 a- and b-type rotational transitions for cis m-cyanophenol and 16 a- and b-type rotational transitions for trans m-cyanophenol. The rotational constants are A = 3408.9200(2) MHz, B = 1205.8269(2) MHz, and C = 890.6672(1) MHz and A = 3403.1196(3) MHz, B = 1208.4903(2) MHz, and C = 891.7241(2) MHz for the cis and trans species, respectively. Rotational transitions of the p-cyanophenol monomer are split due to the internal rotation of the hydroxyl group with respect to the aromatic ring. We recorded 25 a- and b-type rotational transitions for p-cyanophenol; the b-type transitions are split by 40 MHz. The rotational constants are A = 5612.96(2) MHz, B = 990.4283(6) MHz, and C = 841.9363(6) MHz. The ground state spitting DeltaE is 20.1608(6) MHz and the barrier to internal rotation, V(2), is 1413(2) cm(-1) from a fit of the rotational transitions to an internal axis system Hamiltonian. The barrier to internal rotation was modeled at the MP2/6-311++G(d,p) level and the effects of substituents on the phenolic ring and the barriers to internal rotation are discussed.
对 p-、m-和 o-氰苯酚的旋转光谱进行了测量，测量范围为 10.5-21GHz，并使用 Watson 的 A 约化哈密顿量与（14）N 核的核四极耦合相互作用项进行拟合。在 MP2/6-311++G(d,p)和 CCSD(T)/6-311++G(d,p)水平的从头算预测 m-和 o-氰苯酚的顺式构象比相应的反式构象更稳定。o-和 m-氰苯酚中氢键相互作用的自然键轨道分析表明，分子内氢键优先稳定 o-氰苯酚的顺式构象，但 m-氰苯酚的顺式构象中没有氢键相互作用的证据。我们记录了 25 个顺式 o-氰苯酚的 a-和 b-型旋转跃迁；旋转常数为 A = 3053.758(2)MHz，B = 1511.2760(3)MHz，C = 1010.7989(2)MHz。没有观察到 o-氰苯酚的反式构象。我们记录了 14 个 a-和 b-型旋转跃迁的顺式 m-氰苯酚和 16 个 a-和 b-型旋转跃迁的反式 m-氰苯酚。旋转常数为 A = 3408.9200(2)MHz，B = 1205.8269(2)MHz，C = 890.6672(1)MHz 和 A = 3403.1196(3)MHz，B = 1208.4903(2)MHz，C = 891.7241(2)MHz 分别为顺式和反式物种。p-氰苯酚单体的旋转跃迁由于羟基相对于芳环的内部旋转而分裂。我们记录了 25 个 p-氰苯酚的 a-和 b-型旋转跃迁；b-型跃迁分裂了 40MHz。旋转常数为 A = 5612.96(2)MHz，B = 990.4283(6)MHz，C = 841.9363(6)MHz。基态分裂 DeltaE 为 20.1608(6)MHz，内部旋转势垒 V(2)为 1413(2)cm(-1)，这是通过将旋转跃迁拟合到内部轴系哈密顿量得到的。在 MP2/6-311++G(d,p)水平上对内部旋转势垒进行了建模，并讨论了取代基对酚环和内部旋转势垒的影响。
