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Computer modeling of α ‐ to β′ ‐ form phase transitions using theoretical triglyceride structures
Author(s) -
Hagemann James W.,
Rothfus John A.
Publication year - 1988
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/bf02898315
Subject(s) - phase transition , intermolecular force , chain (unit) , rotation (mathematics) , phase (matter) , energy (signal processing) , molecule , excitation , chemical physics , chemistry , crystallography , tilt (camera) , molecular physics , physics , condensed matter physics , geometry , quantum mechanics , mathematics , organic chemistry
Intermolecular energy calculations were performed on theoretical triarachidin α ‐form structures as selected bond rotations converted them into β′ ‐forms with a chain‐tilt change in the glycerol region. Interactions across the methyl gaps amounted to only 2‐3% of the total energy in initial α ‐ and final β′ ‐forms, but computer generated energy profiles during α ‐ to β′ ‐phase transitions revealed highly repulsive regions due to the close approach of methyl groups. This methyl gap interaction, plus additional repulsive interactions in the lateral packing of molecules during rigid chain rotations, necessitated modification of certain chain movements during phase transition to reduce excessive repulsive energy. These results suggest that phase transitions proceed in a particular sequence of events that either distribute energy to promote further phase excitation or that lead to collapse into the stable polymorphic form. Phase transition energy curves also reveal that secondary α ‐ and β′ ‐forms are possible and are dependent on the starting α ‐forms, the direction of chain rotation and the subcell arrangement.