In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
Q: A reagent with two atoms of this element and two of chlorine appears in the Herz reaction, used in dye chemistry. Aryl ketones give amides using an ammonium salt of this element in a reaction whose Kindler modification uses morpholine and its elemental form and which is named for Willgerodt. One method of hydrogen production is a cycle named for this element and iodine. Catalysts with an aromatic ring that includes nitrogen and this heteroatom permits aliphatic aldehydes to undergo a condensation reaction analogous to the benzoin condensation; another example of umpolung is employing the formation of an acetal analogue that includes this element. Bonds between two atoms of this element are cleaved in a reaction named for Zincke. The pseudohalide tosylate is an acid of this element that includes a toluene group. Ylides containing this element are used to form epoxides in the Corey-Chaykovsky reaction. An acid containing this element is synthesized in the contact process. Another functional group containing this element is found in cysteine and was once called mercaptan. For 10 points, name this element in the same group as oxygen with a terrible smell.
A:
Science