Document Detail


Thermodynamics of the Clusterization Process of <i>trans</i>-Isomers of Unsaturated Fatty Acids at the Air/Water Interface.
MedLine Citation:
PMID:  22280464     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
In the frameworks of the quantum-chemical semiempirical PM3 method, the thermodynamic parameters of trans-isomers of unsaturated carboxylic acids at the air/water interface were studied. Systems with 18-26 carbon atoms in the alkyl chain and different positions of the double bond are considered. Using quantum-chemical semiempirical PM3 method enthalpy, Gibbs' energy of monomers' formation from the elementary compounds and absolute entropy of trans-unsaturated carboxylic acids are calculated. It was shown thermodynamic parameters mentioned above for isomers with the same number of carbon atoms in the hydrocarbon chain but different position of double bond are practically the same within the margin of error. For dimers, trimers and tetramers of the four trans-unsaturated carboxylic acids, the thermodynamic parameters of clusterization were calculated. It is shown that the position of double bond does not significantly affect the values of thermodynamic parameters of formation and clusterization of carboxylic acids with equal alkyl chain lengths. The only exception is the case that the double bond is in -position (extremely distanced from the carboxylic group). In this case, the number of intermolecular interactions between alkyl chains is changed. Spontaneous clusterization of trans- in the standard conditions is possible for molecules that possess more than 16-17 carbon atoms in the alkyl chain. These threshold values exceed the corresponding values which were calculated previously using the quantum-chemical PM3 method for saturated carboxylic acids (12-13 carbon atoms in the alkyl chain) and are a little bit smaller than the corresponding parameters for cis-unsaturated carboxylic acids (18-19 carbon atoms). These values agree with experimental parameters. Also the calculated structural parameters of trans-unsaturated carboxylic acids' monolayer for the unit cell with a=6.98 Å, b=8.30 Å and for the molecular tilt angle with 64.95° agree with the experimental parameters.
Authors:
Yuri B Vysotsky; E A Belyaeva; Elena S Fomina; Dieter Vollhardt; Valentin B Fainerman; Reinhard Miller
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-1-26
Journal Detail:
Title:  The journal of physical chemistry. B     Volume:  -     ISSN:  1520-5207     ISO Abbreviation:  -     Publication Date:  2012 Jan 
Date Detail:
Created Date:  2012-1-27     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101157530     Medline TA:  J Phys Chem B     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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