Organization of the enantiomeric and racemic forms of an amphiphilic resorcinol derivative at the air–water and graphite–1‐phenyloctane interfaces

Abstract

This article describes a study of the outcome of racemate condensation in different types of monolayers. The study was performed on a resorcinol surfactant bearing an octadecyl chain and a lactate group which formed a monolayer at the interface of graphite and 1-phenyloctane as well as a Langmuir film at the air-water interface. Control experiments with the enantiopure materials provided the characteristics of the chiral organizations. The results obtained on the racemate show that on graphite the molecule forms chiral domains, indicating that spontaneous resolution takes place at the surface, a phenomenon that has been rationalized using molecular modeling. The X-ray crystal structure of the DMSO solvate of one of the enantiomers shows a similar type of packing to this monolayer. On the other hand, in the Langmuir layer it appears that the formation of a racemic compound is favoured, as it is in the solid state in three dimensions. The work shows how the symmetry restrictions in different environments can have a critical influence on the outcome of racemate organization, and underline the tendency of graphite to favour symmetry breaking in monolayers formed at its surface.

Pasteurian Segregation on a Surface Imaged In Situ at the Molecular Level

“…Compound 1 was synthesized according to the reported procedure, [15] whereas 2 was obtained from Acros (99 %). Mechanically cut tips were used in the measurements (Pt/Ir wire 80 %/20 %, diameter 0.25 mm).…”

“…[15] The octadecyloxy chains favor monolayer formation by physisorption through CÀH···p interactions with HOPG and van der Waals interactions between those chains. [15] The octadecyloxy chains favor monolayer formation by physisorption through CÀH···p interactions with HOPG and van der Waals interactions between those chains.…”

Pasteurian Segregation on a Surface Imaged In Situ at the Molecular Level

“…An alkylated resorcinol derivative ( 1 ) with a lactate moiety, which is the source of chirality, was selected as the potential resolving agent, as the compound itself displays spontaneous resolution on highly oriented pyrolytic graphite (HOPG) 15. The octadecyloxy chains favor monolayer formation by physisorption through CH⋅⋅⋅π interactions with HOPG and van der Waals interactions between those chains.…”

“…Rac ‐1,2‐diaminocyclohexane (a 1:1 mixture of ( R , R )‐ and ( S , S )‐ 2 ) served as the racemate because the amine groups can interact with the hydrogen‐bond donors in the acid group of the resolving agent. The enantiomers of 1 form enantiomorphous monolayers on HOPG when adsorbed from 1‐phenyloctane 15. The individual resorcinol residues can be identified by STM, showing that nearest‐neighbor molecules of different rows form dimers which are organized in lamellae over large areas up to several square micrometers.…”

“…The compounds under investigation were dissolved in 1‐phenyloctane (Aldrich, 98 %). Compound 1 was synthesized according to the reported procedure,15 whereas 2 was obtained from Acros (99 %). The overall concentration of 1 in the solution is always 7.6×10 −3 M while the concentration of 2 is varied from sample to sample depending on the molar ratio of 1 and 2 .…”