the channel long axis, which is a major source for spin-lattice relaxation. Moreover, it is found that the orientation of the methyl groups is perpendicular to the long molecular axis (i.e. gauche conformation at both chain ends) which gives rise to a better molecular packing and stronger van-der-Waals interactions. Activation energies of 24.3 (±1.0) kJ/mol are derived for the overall molecular rotation
摘要 首次对具有双支链烷烃客体分子的尿素包合物进行了固态 2 H- 和 13 C NMR 研究。在两个亚甲基(C3 和 C14 位置)或两个末端异丙基(C1、C1'、C2、C15、C16 和 C16' 位置)上氘化的 2,15-二甲基十六烷的两个样品上进行了变温 2 H NMR 测量)。13 C NMR 数据表明内链段存在于反式构象中。对实验 2 H NMR 数据的综合分析表明,客体分子围绕通道长轴进行受限制的整体旋转(以简并 2 位点跳跃过程建模),这是自旋晶格弛豫的主要来源。而且,发现甲基的方向垂直于分子长轴(即两个链端的 gauche 构象),这会产生更好的分子堆积和更强的范德华相互作用。整个分子旋转的活化能为 24.3 (±1.0) kJ/mol,而甲基旋转值为 14.4 (±0.6) kJ/mol(210 和 250 K 之间)和 12.0 (±1.7) kJ/mol (在 160
Straub,H. et al., Justus Liebigs Annalen der Chemie, 1973, p. 1339 - 1351
作者:Straub,H. et al.
DOI:——
日期:——
Microbiological oxidation of long-chain aliphatic compounds. Part II. Branched-chain alkanes
作者:D. F. Jones
DOI:10.1039/j39680002809
日期:——
of 2,2-dimethylhexadecane occurs exclusively at the less hindered terminal position which is the predominant site of the initial oxidation of 2-methyl-hexadecane. Alkanoicacids and alkan-1-ols which have methyl substituents close to the functional group give ω- and ω-1-hydroxy-derivatives; alkanoicacids and alkan-1-ols which have methyl substituents at the ω-1-position give ω-hydroxy-derivatives