α-羟基羧酸与硼酸的络合反应对其旋光的影响研究
Study on the Effect of the Complex Reaction between Boric Acid and Hydroxycarboxylic Acid on the Optical Rotation of Hydroxycarboxylic Acid
本论文从筛选和设计催化剂的角度,测量硼酸加入后α-羟基羧酸的旋光度的变化,分析络合反应产物种类与配合物构型变化的关系。采用多项式拟合,得到了旋光度与硼酸用量之间的函数。通过对拟合的旋光度函数进行微分求导,得到了旋光度变化率函数。结果表明,当形成配合物时,由于反应成环,电子可极化性增加,配合物的旋光度增加;当形成双配体的配合物时,形成了新的手性中心,但左旋体和右旋体的量相同,新形成的手性中心对旋光度增加贡献率为 0.即:对于旋光度为 0的α-羟基羧酸,加入硼酸后,测得的旋光度仍为 0;对于手性α-羟基羧酸,加入硼酸后旋光度增加,增加值的贡献来自于形成的单配体配合物。按照旋光度的相对变化率排序为:L(+)-酒石酸(267%)≈D(-)-酒石酸(261%)>L-(-)-苹果酸(88%)>D-葡萄糖酸(66%)>(R)-(-)-扁桃酸(13%)>D-(-)-乳酸(-13%),其中D-(-)-乳酸的旋光度的绝对值先减小后增加。旋光度变化率的最小处对应的硼酸与α-羟基羧酸的摩尔比约为 3,此时单配体络合物的相对含量达到最大。继续增加硼酸用量,旋光度变化不大。旋光度变化与pH的变化具有相关性,加入硼酸后形成的配合物种类越多,消耗掉的阴离子就越多,就更容易促进电离平衡向正方向移动。从热力学上来说,配合物的种类越多,熵值增加越大,络合反应越容易进行。
From the perspective of screening and designing catalysts,this paper measured the changes in the optical rotation of hydroxycarboxylic acids after the addition of boric acid,and analyzed the relationship between the types of complexation reaction products and the changes in complex configurations.The polynomial fitting was used to obtain the function between the rotation and the amount of boric acid used.The rate of change function of optical rotation is obtained by differential derivation of the fitted optical rotation function.The results showed that when the complex was formed,the electron Polarizability and the optical rotation of the complex increased due to the ring formation reaction;When a double ligand complex was formed,a new chiral center was formed,but the amount of left-handed and right-handed bodies was the same,and the contribution rate of the newly formed chiral center to the increase in optical rotation was 0.That was,for a rotation of 0 α-hydroxycarboxylic acid,after adding boric acid,the measured optical rotation remained 0;For chirality α-hydroxycarboxylic acid,with the addition of boric acid,the optical rotation increased,and the contribution of the added value comes from the formation of single ligand complexes.According to the relative change rate of optical rotation,the order is:L(+)-Tartaric acid(267%)≈ D-(-)-Tartaric acid(261%)>L-(-)-Malic acid(88%)>D-Gluconic acid(66%)>(R)-(-)-Mandelic acid(13%)>D-(-)-lactic acid(-13%),where the absolute value of optical rotation of D-(-)-lactic acid first decreased and then increased.The molar ratio of boric acid to α-hydroxycarboxylic acid corresponding to the minimum rate of rotation change was about 3,at which point the relative content of the single ligand complex reaches its maximum.Continue to increase the amount of boric acid,but the change in optical rotation was not significant.There was a correlation between changes in optical rotation and changes in pH.The more types of complexes formed after the addition of boric acid,the more anions consumed,and it was easier to promote the positive shift of ionization equilibrium.From a thermodynamic perspective,the more types of complexes,the greater the entropy increased,and the easier the complexation reaction to occur.
孟中磊;秦荣秀;黎贵卿;陈海燕;
广西优良用材林资源培育重点实验室/广西壮族自治区林业科学研究院,广西 南宁,530002;广西优良用材林资源培育重点实验室/广西壮族自治区林业科学研究院,广西 南宁,530002;广西优良用材林资源培育重点实验室/广西壮族自治区林业科学研究院,广西 南宁,530002;广西优良用材林资源培育重点实验室/广西壮族自治区林业科学研究院,广西 南宁,530002;
α-Hydroxycarboxylic acid Boric acid Complexation reaction Corresponding isomers Optical rotation
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