This element attacks a carbon singly-bonded to this element in the first step of native chemical ligation. This element is the central nonmetal in a compound that reacts with oxalyl chloride in the beginning of the Swern oxidation. This element (-5[1])substituted with two methyl groups is doubly-bonded to an oxygen in a common organic solvent. (10[1])Clusters of iron and this element are widely present (10[1])in enzymes (10[1])that mediate biochemical electron transfers. Cross-links with this element are created in vulcanization. (10[1])This element bonded (10[1])to (10[1])itself (10[1])creates a namesake “bridge,” and this element bonded to hydrogen forms a thiol group, such as that in cysteine. For 10 points, name this chalcogen found under oxygen in the periodic table, which has a characteristic odor of rotten eggs. ■END■