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Adsorption of dimer, trimer, stearic, oleic, linoleic, nonanoic and azelaic acids on ferric oxide
Author(s) -
Wheeler D. H.,
Potente D.,
Wittcoff Harold
Publication year - 1971
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02545734
Subject(s) - chemistry , adsorption , trimer , dimer , azelaic acid , stearic acid , organic chemistry , moiety , oleic acid , inorganic chemistry , biochemistry
The adsorption isotherms of solutions of dimer, trimer, stearic, oleic, linoleic, nonanoic and azelaic acids in organic solvents, (mostly hexane) have been determined on an alpha ferric oxide with a surface area (B.E.T. N 2 adsorption) of 99 m 2 (99 × 10 20 A 2 ) per gram. They all showed limiting adsorption as grams adsorbed per gram of iron oxide beyond a concentration of about 1 g/100 cc, analagous to the Langmuir type monolayer isotherm. Areas per molecule were calculated and compared with areas of close‐packed models in positions parallel to and perpendicular to the surface. The calculated areas corresponded more closely to the flat or parallel positions. Heats of adsorption were determined and were in the range of 27–71 kcal/eq, suggesting chemisorption of the COOH group at the surface. The value of dimer acid suggests that both COOH groups are chemisorbed. Models show that the parallel position permits both COOH groups to touch the surface. The perpendicular position generally does not permit both COOH groups to touch the surface. Dimer acid showed a value (71 kcal/eq) higher than the monobasic acids (44–55 kcal/eq), possibly due to interaction of the ring structure (partly aromatic) with the surface. Azelaic acid from an 80–20 t ‐butanol‐hexane solvent showed a lower value of 27 kcal/eq, possibly due to adsorption of a hydrogenbonded alcohol‐acid moiety as such.