已入深夜,您辛苦了!由于当前在线用户较少,发布求助请尽量完整地填写文献信息,科研通机器人24小时在线,伴您度过漫漫科研夜!祝你早点完成任务,早点休息,好梦!

Tautomeric Equilibrium of Pyridoxine in Water. Thermodynamic Characterization by 13C and 15N Nuclear Magnetic Resonance

互变异构体 化学 化学位移 热力学 化学平衡 物理化学 立体化学 物理
作者
Juan Llor,Luís Múñoz
出处
期刊:Journal of Organic Chemistry [American Chemical Society]
卷期号:65 (9): 2716-2722 被引量:20
标识
DOI:10.1021/jo991821t
摘要

A remarkable temperature dependence on the 13C NMR and 15N NMR chemical shifts of pyridoxine in water (pH = 7.0) has been observed. C-3, C-6, and N-1 were the most sensitive nuclei to the temperature effect. This dependence has been explained on the basis of an equilibrium shift thermally induced between the neutral and the dipolar form of this molecule. The thermodynamic characterization of tautomeric equilibria that interconvert quickly on the NMR time scale can be carried out from the observed average 13C NMR and 15N NMR chemical shifts at different temperatures (5−90 °C). We have developed a new method for the estimation of the thermodynamic parameters of a given equilibrium by fitting the experimental data to a theoretical curve. This new method allows us to improve the fitting results on our previously proposed methodology. We show that there are linear correlations between the average chemical shifts obtained from different nuclei at the same temperature. This indicates that the parameters of the pure forms are related among them. We have carried out a simultaneous multiple function curve fitting of all data obtained from the most sensitive signals together using these linear correlations as restricted conditions in order to diminish the number of independent parameters to fit. To test the new methodology, we have studied the thermodynamics of the tautomeric equilibrium of pyridoxine in water. We have obtained ΔH° values ranging from −23.6 ± 1.3 to −25.8 ± 1.7 kJ/mol for this equilibrium depending on the used data set. This kind of methodology has, among others, the following advantages: It allows the use of a great number of experimental points from different signals in the fitting process, it yields very precise and accurate values of the tautomeric process, and it allows the resolution of the problem with only 13C NMR data in some cases saving NMR time.
最长约 10秒,即可获得该文献文件

科研通智能强力驱动
Strongly Powered by AbleSci AI
更新
PDF的下载单位、IP信息已删除 (2025-6-4)

科研通是完全免费的文献互助平台,具备全网最快的应助速度,最高的求助完成率。 对每一个文献求助,科研通都将尽心尽力,给求助人一个满意的交代。
实时播报
HuLL完成签到 ,获得积分10
刚刚
在水一方应助科研通管家采纳,获得10
2秒前
2秒前
Pauline完成签到 ,获得积分10
3秒前
wch666发布了新的文献求助10
15秒前
16秒前
Lion完成签到,获得积分10
18秒前
星辰大海应助科研达人采纳,获得10
18秒前
冰糖葫芦娃完成签到,获得积分10
20秒前
momo应助Lion采纳,获得10
22秒前
22秒前
23秒前
干净涵梅完成签到,获得积分10
27秒前
Calyn完成签到 ,获得积分0
33秒前
高兴的忆曼完成签到,获得积分10
37秒前
淡淡的向雁完成签到,获得积分10
40秒前
52秒前
xiaolang2004完成签到,获得积分10
53秒前
胡萝卜完成签到,获得积分10
58秒前
专一的咖啡完成签到,获得积分10
1分钟前
Akim应助hume采纳,获得10
1分钟前
yuan完成签到 ,获得积分10
1分钟前
akakns完成签到 ,获得积分10
1分钟前
罐罐完成签到,获得积分10
1分钟前
六六完成签到 ,获得积分10
1分钟前
1分钟前
1分钟前
直觉应助科研达人采纳,获得10
1分钟前
Cain完成签到,获得积分10
1分钟前
叮当拉卡给叮当拉卡的求助进行了留言
1分钟前
和谐的冬莲完成签到 ,获得积分10
1分钟前
Li发布了新的文献求助10
1分钟前
水若琳发布了新的文献求助10
1分钟前
隐形曼青应助背后的鞋垫采纳,获得10
1分钟前
lab完成签到 ,获得积分0
1分钟前
wch666完成签到,获得积分10
1分钟前
GingerF完成签到,获得积分0
1分钟前
NZC完成签到,获得积分10
1分钟前
luroa完成签到 ,获得积分10
2分钟前
英俊的铭应助风吹屁屁凉采纳,获得10
2分钟前
高分求助中
The Mother of All Tableaux: Order, Equivalence, and Geometry in the Large-scale Structure of Optimality Theory 3000
A new approach to the extrapolation of accelerated life test data 1000
ACSM’s Guidelines for Exercise Testing and Prescription, 12th edition 500
Indomethacinのヒトにおける経皮吸収 400
Phylogenetic study of the order Polydesmida (Myriapoda: Diplopoda) 370
基于可调谐半导体激光吸收光谱技术泄漏气体检测系统的研究 350
Robot-supported joining of reinforcement textiles with one-sided sewing heads 320
热门求助领域 (近24小时)
化学 材料科学 医学 生物 工程类 有机化学 生物化学 物理 内科学 纳米技术 计算机科学 化学工程 复合材料 遗传学 基因 物理化学 催化作用 冶金 细胞生物学 免疫学
热门帖子
关注 科研通微信公众号,转发送积分 3990008
求助须知:如何正确求助?哪些是违规求助? 3532034
关于积分的说明 11256121
捐赠科研通 3270913
什么是DOI,文献DOI怎么找? 1805105
邀请新用户注册赠送积分活动 882270
科研通“疑难数据库(出版商)”最低求助积分说明 809216