Detection of secondary alkanols in Neogene sediments of the Shinjo basin, Japan : possible thermal hydration reaction products

概要

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C_<14> to C_<28> n-alkan-1-ols, together with C_<14>-C_<31> n-alkan-2-ols, C_<14>-C_<29> n-alkan-3-ols, C_<20>-C_<29> n-alkan-4-ols, C_<14>-C_<27> n-alkan-5-ols and C_<14>-C_<24> n-alkan-6-ols were identified in Neogene sediments from Shinjo basin, Yamagata Prefecture, Japan. Total amounts of n-alkan-1-ols tended to decrease from 50μg/gC in the uppermost section to 13μg/gC in the lower sections, whereas those of 2-ols and 3-ols slightly increased in the middle and then decreased in the lower sections. On the contrary, n-alkan-4-ols, n-alkan-5-ols and n-alkan-6-ols were absent or negligibly small in the upper sections and detectable only in the middle to lower sections. Primary alkanols, n-alkan-1-ols, had a peak maximum at C_<16> or C_<18> and showed a small but evident even carbon-number preference particularly in the range of C_<14>-C_<20>. On the other hand, secondary alkanols, exemplified by n-alkan-2-ols had no significant even-odd preference and the peak maximum, being at C_<13>-C_<15> in the upper sections appeared to shift gradually to longer chain homologues. Since it is known that the middle to lower sections of this sedimentary sequence correspond to the hydrocarbon expulsion stage, those secondary alkanols are considered to be the intermediate by-products of the isomerization and hydration of alkenes generated by thermal cleavage of long-chain moieties incorporated within kerogen matrix.
日本有機地球化学会の論文
2004-12-30