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A dimer () (''di-'', "two" + ''-mer'', "parts") is an oligomer consisting of two structurally similar monomers joined by bonds that can be either strong or weak, covalent or intermolecular. The term ''homodimer'' is used when the two molecules are identical (e.g. A-A) and ''heterodimer'' when they are not (e.g. A-B). The reverse of dimerisation is often called dissociation. == Noncovalent dimers == Carboxylic acids form dimers by hydrogen bonding of the acidic hydrogen and the carbonyl oxygen when anhydrous. For example, acetic acid forms a dimer in the gas phase, where the monomer units are held together by hydrogen bonds. Under special conditions, most OH-containing molecules form dimers, e.g. the water dimer. Borane ("BH3") occurs as the dimer diborane (B2H6), due to the high Lewis acidity of the boron center. Excimers and exciplexes are excited structures with a short lifetime. For example, noble gases do not form stable dimers, but do form the excimers Ar2 *, Kr2 * and Xe2 * under high pressure and electrical stimulation. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Dimer (chemistry)」の詳細全文を読む スポンサード リンク
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