THERMODYNAMIC STABILITY OF VARIOUS ALKYLATED, DEALKYLATED AND REARRANGED 17-ALPHA-HOPANE AND 17-BETA-HOPANE ISOMERS USING MOLECULAR MECHANICS CALCULATIONS

被引:96
作者
KOLACZKOWSKA, E
SLOUGUI, NE
WATT, DS
MARUCA, RE
MOLDOWAN, JM
机构
[1] CHEVRON OIL FIELD RES CO,RICHMOND,CA 94802
[2] ALDERSON BROADDUS COLL,DEPT CHEM,PHILIPPI,WV 26416
关键词
OBSERVED VS CALCULATED; BIOMARKER RATIOS; MOLECULAR MECHANICS (MM2); CALCULATIONS; CONFORMATIONAL ISOMERS; 17-ALPHA AND 17-BETA HOPANES; ALKYLATED HOPANES; DEALKYLATED HOPANES;
D O I
10.1016/0146-6380(90)90140-U
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The thermodynamic stability of selected alkylated, dealkylated and rearranged 17-alpha- and 17-beta-hopane isomers in the C27, C28, C29, C30 and C31 families were calculated using molecular mechanics (MM2) methods and, where possible, calculated equilibrium ratios of certain isomers were compared with observed ratios of isomers in thermally mature crude oil samples. Those calculated and observed ratios having similar values include: (1) the relative distributions among 17-beta-(H)/17-alpha-(H) and 21-beta-(H)/21-alpha-(H)-hopanes including the absence of the 17-beta-(H),21-beta-(H)- and 17-alpha-(H),21-alpha-(H)-hopanes; (2) the 22R/22S ratios in 30-methyl-17-alpha-hopane and 30-methyl-17-beta-moretane; (3) the relative distributions among 17-alpha-(H)/17-beta-(H)- and 21-alpha-(H)/21-beta-(H)-28, 30-bisnorhopanes and among 25,28,30-trisnorhopanes, including the relatively greater stability of 17-beta-(H) isomers in contrast to the regular hopane series; and (4) the ratios of 28(18-17S)abeo hopanes with respect to their unrearranged counterparts including the C27 compounds, Ts/Tm.
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页码:1033 / 1038
页数:6
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