本論文藉由ab initio理論計算的方法，在HF及MP2層次下，使用6-31+G**基底群，對各穩定點及其相對應過渡結構做全面性的幾何優選，以探討氧□酸及其衍生物做分子內質子轉移時的各項性質，最終相對能量的決定，則使用MP2/6-31++G**//MP2/6-31+G** 或G2理論。共分為以下四個單元進行研究：
第一單元 研究氧□酸中最簡單的分子形式Formohydroxamic acid (H-HA)。研究結果發現H-HA主要有5種異構物，以keto form 且具分子內氫鍵的1Znp最為穩定。5種異構物之間的轉換，是由氮上的質子或氧上的質子轉移所構成，總共有３條分子內質子轉移的路徑，分別會經過三環、四環和五環的過渡結構，其能障分別為50.8、42.4 、12.9 kcal/mol.由分子內質子轉移位能曲線判斷H-HA在氣態的狀態下應是N上的氫解離（N-acid），分子內氫鍵和偶極矩作用力是影響H-HA酸性強度的兩大原因。
第二單元 研究氧□酸的另二個分子：acetohydroxamic acid(M-HA) 和fluorohydroxamic acid(F-HA)，這二者是從H-HA醛基上的H分別取代成CH3和F而來，探討推電子基（CH3）和拉電子基（F）對H-HA做分子內質子轉移的影響。研究的結果發現取代基確實對質子的親和力、偶極矩的大小及方向、質子轉移的能障均有決定性的影響。推電子取代基時，各路徑的活化能均降低；拉電子取代基時，各路徑的活化能均上升。Hydroxamic acids(HAs)在相同質子轉移路徑下，牽扯到質子轉移時的目的原子和起始原子這二個重原子所移動的距離長短和能障的高低有高度的相關性。
第三單元 研究的是formyl-hydroxyl phosphine (FHP), FHP是把H-HA的N改成P而來，研究結果發現它和H-HA一樣仍具有５種異構物，以keto form且具分子內氫鍵的PIZnp最為穩定。FHP有三種分子內質子轉移路徑，是由磷上或氧上的質子轉移所構成，從轉移的位能曲面判斷，知道FHP在氣相的狀態下，應該是P上的氫解離較為容易，為P-acid。FHP的酸解離能是337.1 kcal/mol ，比H-HA、M-HA強，主要的原因是P較N有較大的體積，容易分散解離氫後的陰離子電荷，穩定陰離子，解離能自然較高。FHP質子轉移的能障都比H-HA高，主要的原因是因為P的原子體積較大，撐開了質子轉移時目的原子和起始原子的二重原子距離，而使得質子轉移時所需移動的距離增加，所以能障增加。
第四單元 研究分別在H-HA和FHP的異構物中加入一分子水。研究的結果發現H-HA在有一分子水參與的情況下，其質子轉移的活化能，除了在（A）途徑些微上升了0.2kcal/mol之外，其餘均降低，尤其在（C）途徑大幅降低了24.6kcal/mol.很明顯的，在（C）途徑活化能降低的幅度，比（A）途徑大了許多，主要的原因是（C）途徑的過渡結構本來從立體障礙最大的四環結構，在一分子水加入後變成了穩定度最高的六環結構，穩定度大幅增加；而相對的（A）途徑卻是從立體障礙不大的五環，變成了穩定度不很好的七環，穩定度變動不大，所以（C）途徑活化能的降低幅度，會比（A）途徑大了許多。活化能的改變值，等於過渡結構和水的結合能減去位能低點和水的結合能。

This dissertation deals with the properties of intramolecular proton transfer of hydroxamic acid and its dervatives by ab initio methods.Each tautomer and its corresponding TS are fully optimized with 6-31+G** basis sets at the levels of HF and MP2.Relative energies of species are finally evaluated at MP2/6-31++G**//MP2/6-31G** or G2 theory.There are four sections rendered here.
Section 1: Formohydroxamic acid (H-HA), which is the simplest form of hydroxamic aicd (HAs), is studied firstly.H-HA is found to have five tautomers, among which the 1Znp form, a keto form, having intra-molecular hydrogen bond is the most stable one.The intra-proton transfer among the five tautomers is initiated by the proton connected on the nitrogen or oxygen. There are three possible pathways of intramolecular proton transfer, each of which has the transition structure of 3-, or 4-, or 5- member ring, individually with its energy barrier 50.8, 42.4, 12.9 kcal/mol at G2 theory, respectively. Based on the potential energy surface of intramolecular proton transfer, we concluded that H-HA is an N-acid in the gas phase and the strength of its acidity is affected by two major factors－－intramolecular hydrogen bond, and the dipole-dipole interaction.
Section 2: Another two forms of HAs, acetohydroxamic acid (M-HA) and fluorohydroxamic acid (F-HA),are studied secondly.They are generated by the replacement of hydrogen in the aldehyde group of H-HA with CH3 and Fatom, respectively, The purpose of this section is to study the influence of electron-withdraawing and electron-releasing substituents on proton affinities, on the magnitude and direction of dipole moments and on proton-transfer barriers.The presence of the methyl substituent decreases the proton-transfer barrier, while that of the fluorine substituent increases it.The barrier is also highly correlated with the distance between two heavy atoms within which the proton transfer takes palce.
Section 3: Formyl-hydroxyl phosphine (FHP) is studied thirdly.The N atom in H-HA is replaced with P atom, FHP is also found to have five tautomers and the PIZnp form similar to 1Znp form of H-HA is the most stable one.There are also three possible pathways of intramolecular proton transfer, each of which has the transition structures of 3-, or 4-, or 5- member ring ,individually, with the energy barrier 67.0, 28.9, 51.4 kcal/mol at MP2 S.P. calculation, respectively. All barriers of FHP on the corresponded three proton-transfer pathways are higher than H-HA ,This is because of the bigger volume of P than N,which extends the distance between two heavy atoms within which the proton is shifted.Therefore, the proton must move farther and increase the energy barrier.The proton could be transferred from the oxygen of phosphorus.Based on the calculated potential energy surface of the intramolecular proton transfer, the proton favors being transferred from phosphorus atom and we concluded that FHP is an P-acid in the gas phase.The △Goacid of FHP is 337.1 kcal/mol, which is smaller than H-HA (339.6 kcal/mol) and M-HA (341.1 kcal/mol), due to the face that P atom is bigger than N atom, and the distributed negative charge density from the dissociated proton is much smaller.
Section 4: Finally, we focused our study on the water assisted proton transfer in monohydrated H-HA and FHP, denoted as H-HA:W and FHP:W. The result show that Adding one water molecule reduces the barrier of proton transfer, except in path (A) of H-HA:W complex with a little increase of 0.2 kcal/mol. The barrier decreases largely 24.6 kcal/mol in path (C) of H-HA:W complex. The amount of the activation decreasing in path (C) is larger than in path (A). In path (C), the transition structure changes from the 4-member ring to the 6-member ring in monohydrated form. The 4-member ring structure is highly strained, compared to the 6-member ring structure.In contrast, in path (A), the transition structure changes from a less strained 5- member ring to a 7-member ring which does not gain any stability, Consequently, the decrease of barrier is considerable in path (C), but few in path (A).