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Polymorphism in single‐acid triglycerides of positional and geometric isomers of octadecenoic acid
Author(s) -
Hagemann J. W.,
Tallent W. H.,
Barve J. A.,
Ismail I. A.,
Gunstone F. D.
Publication year - 1975
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/bf02672171
Subject(s) - differential scanning calorimetry , double bond , chemistry , polymorphism (computer science) , cis–trans isomerism , fusion , melting point , single bond , stereochemistry , crystallography , enthalpy of fusion , group (periodic table) , organic chemistry , thermodynamics , physics , biochemistry , linguistics , gene , genotype , philosophy
The polymorphism of 25 glycerol trioctadecenoates with double bonds ranging from Δ4‐Δ17 was investigated by differential scanning calorimetry. Triglycerides with cis bonds in odd positions Δ7‐Δ13 exhibited three intermediate melting (β′‐) forms, but those with cis bonds in even positions, except cis Δ4, lacked β′‐forms. Among the trans compounds, only Δ11, 13, and 14 showed β′‐forms. The cis and trans Δ5 triglycerides were unusual, because they readily assumed low melting (α‐) forms that were not easily converted to high melting (β‐) forms. β‐Form mp of compounds in each series ( cis or trans ) alternated depending upon double bond position; an even position correlated with high mp. Heats of fusion (ΔH f ) for β‐forms, likewise, fluctuated with double bond position but nonuniformly; trans Δ6 had the highest ΔH f (43 cal/g), cis Δ12 the lowest (21 cal/g).