高等学校化学学报
高等學校化學學報
고등학교화학학보
CHEMICAL JOURNAL OF CHINESE UNIVERSITIES
2014年
2期
384-388
,共5页
烟酰胺%异烟酰胺%KCl水溶液%稀释焓%焓对自缔合作用%等温滴定微量热法
煙酰胺%異煙酰胺%KCl水溶液%稀釋焓%焓對自締閤作用%等溫滴定微量熱法
연선알%이연선알%KCl수용액%희석함%함대자체합작용%등온적정미량열법
Nicotinamide%Isonicotinamide%Aqueous KCl solution%Dilution enthalpy%Enthalpic pairwise self-association%Isothermal titration microcalorimetry( ITC)
利用等温滴定微量热法( ITC)分别测定了298.15 K时烟酰胺( NA)和异烟酰胺( INA)在纯水及不同浓度KCl( m=0~0.3 mol/kg)水溶液中的稀释焓，根据McMillan-Mayer理论计算得到相应的焓对自缔合作用系数( hxx )，发现两者的hxx都是很大的负值，且在较高KCl浓度时都随KCl浓度的增大而减小.从溶质-溶质、溶质-溶剂相互作用的观点出发，对这2种吡啶羧酸酰胺异构体的疏水和亲水作用平衡进行了讨论： NA和INA都是亲水-亲水作用占优势，芳香性的吡啶环与酰胺基团羰基的仔电子共轭使得对位异构体的共振结构分子电荷分离而更具亲水性；吡啶环之间的仔-仔堆叠对焓对自缔合作用的贡献几乎可忽略；溶液离子强度( I)的增大有利于加强亲水-亲水作用，从而使hxx的绝对值都随溶液中KCl浓度的增大而逐渐增大.
利用等溫滴定微量熱法( ITC)分彆測定瞭298.15 K時煙酰胺( NA)和異煙酰胺( INA)在純水及不同濃度KCl( m=0~0.3 mol/kg)水溶液中的稀釋焓，根據McMillan-Mayer理論計算得到相應的焓對自締閤作用繫數( hxx )，髮現兩者的hxx都是很大的負值，且在較高KCl濃度時都隨KCl濃度的增大而減小.從溶質-溶質、溶質-溶劑相互作用的觀點齣髮，對這2種吡啶羧痠酰胺異構體的疏水和親水作用平衡進行瞭討論： NA和INA都是親水-親水作用佔優勢，芳香性的吡啶環與酰胺基糰羰基的仔電子共軛使得對位異構體的共振結構分子電荷分離而更具親水性；吡啶環之間的仔-仔堆疊對焓對自締閤作用的貢獻幾乎可忽略；溶液離子彊度( I)的增大有利于加彊親水-親水作用，從而使hxx的絕對值都隨溶液中KCl濃度的增大而逐漸增大.
이용등온적정미량열법( ITC)분별측정료298.15 K시연선알( NA)화이연선알( INA)재순수급불동농도KCl( m=0~0.3 mol/kg)수용액중적희석함，근거McMillan-Mayer이론계산득도상응적함대자체합작용계수( hxx )，발현량자적hxx도시흔대적부치，차재교고KCl농도시도수KCl농도적증대이감소.종용질-용질、용질-용제상호작용적관점출발，대저2충필정최산선알이구체적소수화친수작용평형진행료토론： NA화INA도시친수-친수작용점우세，방향성적필정배여선알기단탄기적자전자공액사득대위이구체적공진결구분자전하분리이경구친수성；필정배지간적자-자퇴첩대함대자체합작용적공헌궤호가홀략；용액리자강도( I)적증대유리우가강친수-친수작용，종이사hxx적절대치도수용액중KCl농도적증대이축점증대.
Dilution enthalpies of nicotinamide and isonicotinamide in pure water and aqueous KCl solutions of various molality(m=0-0. 3 mol/kg) were determined at 298. 15 K by isothermal titration microcalorimetry (ITC). The corresponding values of enthalpic pairwise self-association coefficient(hxx) were evaluated accor-ding to the McMillan-Mayer theory. From the point of view of solute-solute and solute-solvent interactions, the equilibrium between hydrophobic and hydrophilic interactions of the two pyridinecarboxamides was discussed. It is found that both of the hxx values of the two isomers are all largely negtive, and decrease rapidly with in-creasing molalities of KCl at its higher concentrations. It is concluded that both of them are characterized by prevailing hydrophilic-hydrophilic interaction, and that the π-electronic conjugation between aromatic pyridyl ring and carbonyl of amide group makes resonance structure molecule of the para-isomer be more hydrophilic due to charge separation. The results also indicate that the contribution from π-π packing between pyridyl rings can be neglected nearly, and that the increase of ionic strength I favors hydrophilic-hydrophilic interac-tion greatly since both of the hxx absolute values of the two amides increase gradually with the increasing mola-lity of KCl in solutions.
