光分解甲氧基苯甲酸與三氟甲基苯酚之分子內氫鍵效應

Abstract

分子內氫鍵的存在會影響到化合物的能階結構，因此本實驗利用鄰、間、對－甲氧基苯甲酸與鄰、間、對－三氟甲基苯酚在光分解雷射193nm與游離雷射118nm的條件下，於多重離子影像偵測儀進行觀測，藉此探討分子內氫鍵對於分子光分解反應產生的影響。因為鄰、間、對－甲氧基苯甲酸皆無分子內氫鍵，所以一開始主要的反應途徑為甲基解離，之後，由於甲基解離的鄰－甲氧基苯甲酸可以形成分子內氫鍵，以致於分子會進一步地二次分解出CO2。另外，鄰－三氟甲基苯酚具有分子內氫鍵，其光分解反應途徑包括：(1)C6H4OHCF3→C6H4OCF3 + H (2) C6H4OHCF3→C6H4OCF2 + HF，相較於間、對－三氟甲基苯酚而言，多出HF解離的反應途徑。The photodissociation of o-, m-, p-methoxybenzoic acid and o-, m-, p- trifluoromethyl phenol was studied separately in a molecular beam at 193nm using multimass ion image techniques. The major dissociation channel for the first three compounds is CH3 elimination owing to no intramolecular hydrogen bond formation, but o-methoxybenzoic acid will generate intramolecular hydrogen bond after CH3 elimination and cause secondary dissociation to lose CO2. On the other hand, the dissociation channel was observed for o-trifluoromethyl phenol, including (1)C6H4OHCF3→C6H4OCF3 + H ;(2)C6H4OHCF3→C6H4OCF2 + HF. In comparison with photodissociation of m-trifluoromethyl phenol and p-trifluoromethyl phenol, the HF elimination channel is due to the intramolecular hydrogen bond.