Figure 1
(a) The basic forms of the cyclic dimer OC (left) and OH (right), observed in 2-hydroxy-1-cyclopentane- (n = 1), -cyclohexane- (n = 2),-cycloheptane- (n = 3) and -cyclooctane- (n = 4) carboxylic acids. In general, R = H or an alkyl group. (b) Symbolic form: straight lines represent OH groups, small triangles (in carboxamides) represent NH2 groups and circles represent OC groups. (c) To distinguish between the enantiomers, the stick symbols are converted into black or white triangles. (d) The symbolic dimers are held together by hydrogen bonds depicted as -·-·-> (OH⋯O=C) and ···> (XH⋯OH) (X = O in COOH or NH in CONH2). In carboxamides (8T*), the third hydrogen bond (XH⋯O=C) is denoted by --->. |