Reductive alkylation of petroleum residua using potassium metal and tetrahydrofuran at room temperature

Abstract

Two petroleum residua from the same source, one of distillation cutpoint 510 °C (950 °F) and one of cutpoint 704 °C (1300 °F), were placed in THF and reacted with potassium metal at room temperature for 24 h. The consumption of K metal was 4.1–5.0 mmol K (g resid) 2 for the 510 °C −1 resid, and 3.7–3.9 m mol g −1 for the 704 °C + resid. Although both resids showed a (002) peak in X-ray diffraction, alkylation of the resid anions with either methyl or hexyl iodides removed this feature, proving that reductive alkylation does disrupt the stacking of aromatic entities. Sequential reductive alkylations were performed on the 510 °C + resid, first with CD 3I and second with 13C-enriched CH 3I. N.m.r. shows that CD 3S thioethers formed after the first reductive alkylation are completely destroyed after the second reductive alkylation, but that new 13CH 3S thioethers are formed after the second reductive alkylation. This behaviour is completely unlike that known for dibenzothiophene under identical chemical conditions.