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Retardation effect of jojoba chain length on the chemical reactivity of the liquid wax
Author(s) -
Gorodetsky Aleksandra,
Zeltser Inna,
Shani Ar
Publication year - 2005
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/s11746-005-1080-7
Subject(s) - chemistry , steric effects , epoxide , wax , nucleophile , yield (engineering) , steroid , pinacol , medicinal chemistry , derivative (finance) , side chain , organic chemistry , stereochemistry , catalysis , biochemistry , materials science , polymer , hormone , economics , financial economics , metallurgy
Jojoba wax and its derivatives are slow‐reacting compounds. To elucidate the reasons for this phenomenon, we reacted jojoba mono‐ and bis‐epoxide and trans ‐jojoba bis‐epoxide (C 38 –C 44 long‐chain esters), as well as side chain esters of three steroid skeleton mono‐epoxide derivatives with NaI under acidic conditions to yield the corresponding iodohydrins, which then formed the respective bis‐keto (or mono‐ketone) derivatives. The kinetics, activation energies, and thermodynamic parameters of activation of nucleophilic epoxide opening and pinacol rearrangement were determined for all these compounds. The reaction rates of the jojoba derivatives were similar to those of two of the epoxides derived from the steroid skeleton compounds, and in the third case the steroid derivative reacted somewhat faster than all the rest. This pattern of rate retardation could stem either from folding of the long jojoba chain, resulting in steric hindrance around the reaction centers, or from repeated unproductive collisions along the long hydrocarbon chain of the jojoba wax (statistical effect). Our results appear to suggest that the multiple unsuccessful collisions were the dominant factor, although steric hindrance cannot be ruled out.