Left Schematic representation of the two conformations adopted by the carboxyl group of n-carboxylic acids (n-dodecanoic acid is used as an example here) upon adsorption on a graphite surface. (a) The alkyl tail is eclipsed by the hydroxyl group. a is the angle between the hydroxyl group and the long molecular axis. Two n-dodecanoic acid molecules adopting this conformation are shown lying on top of a graphite lattice. (b) The alkyl tail is eclipsed by the carboxyl group. b is the angle between the hydroxyl group and the long molecular axis. Two n-dodecanoic acid molecules adopting this conformation are shown lying on top of a graphite lattice.

For more detail, see: Fang et al., J. Phys. Chem. B, Vol. 103, No. 2, pg. 5712-5715.

Left (a) A 12 x 12 nm2 STM constant current image of 12-bromododecanoic acid at the interface of a phenyloctane solution and the basal plane of graphite. Two parallelograms outline two molecules hydrogen bonded through their carboxyl group, which are offset by half a molecular width. The angle a=­AOB is that between the direction of the hydrogen bond (OB) and the long molecular axis (OA). (b) Top view of a computer-generated model of a 12-bromododecanoic acid film on a graphite substrate. Yellow represents bromine atoms, green represents carbon atoms, gray represents hydrogen atoms, and red represents oxygen atoms. The two parallelograms indicate two molecules hydrogen bonded through their carboxyl groups. (c) A 12 x 12 nm2 STM constant current image of (R)-2-bromohexadecanoic acid at the interface of a phenyloctane solution and the basal plane of graphite. Two parallelograms outline two molecules hydrogen bonded through their carboxyl groups, which are offset by a whole molecular width. The angle b=­COD is that between the direction of the hydrogen bond (OD) and the long molecular axis (OC). (d) Top view of a computer-generated model of an (R)-2-bromohexadecanoic acid film on a graphite substrate. The colors have the same meaning as those in (b).

For more detail, see: Fang et al., J. Phys. Chem. B, Vol. 103, No. 2, pg. 5712-5715.