Baisch Ulrich, Scicluna Marie Christine, Näther Christian, Vella-Zarb Liana
Department of Chemistry, University of Malta, Msida, MSD 2080, Malta.
Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str 2, 24118 Kiel, Germany.
Acta Crystallogr E Crystallogr Commun. 2017 Jan 13;73(Pt 2):155-158. doi: 10.1107/S2056989017000238. eCollection 2017 Feb 1.
The crystal structure of 5-methyl-salicyl-aldehyde (; systematic name 2-hy-droxy-5-methyl-benzaldehyde), CHO, was discovered to be a textbook example of the drastic structural changes caused by just a few weak C-H⋯O inter-actions due to the additional methyl-ation of the aromatic ring compared to salicyl-aldehyde . This weak inter-molecular hydrogen bonding is observed between aromatic or methyl carbon donor atoms and hydroxyl or aldehyde acceptor oxygen atoms with (⋯) = 3.4801 (18) and 3.499 (11) Å. The mol-ecule shows a distorted geometry of the aromatic ring with elongated bonds in the vicinity of substituted aldehyde and hydroxyl carbon atoms. The methyl hydrogen atoms are disordered over two sets of sites with occupancies of 0.69 (2) and 0.31 (2).
5-甲基水杨醛（系统命名为2-羟基-5-甲基苯甲醛）CHO的晶体结构被发现是一个典型案例，表明与水杨醛相比，由于芳环额外甲基化导致的少数弱C-H⋯O相互作用会引发剧烈的结构变化。在芳香族或甲基碳供体原子与羟基或醛基受体氧原子之间观察到这种弱分子间氢键，键长（⋯）分别为3.4801 (18) Å和3.499 (11) Å。该分子的芳环几何形状发生扭曲，在取代醛基和羟基碳原子附近的键伸长。甲基氢原子在两组位置上无序分布，占有率分别为0.69 (2) 和0.31 (2)。
