甲基组在水中的阿里法胺之间迁移
Brian P Callahan1, Richard Wolfenden
1Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, 27599-7260, USA.
Journal of the American Chemical Society
|January 9, 2003
概括
甘氨酸脱碳化产生甲基胺,这些甲基胺进一步反应. 甲基胺在水中发生不成比例,产生其他甲基胺,这是化学动力学的新发现.
科学领域:
- 有机化学 有机化学
- 化学动力学 化学动力学
- 反应机制 反应机制
背景情况:
- 在高温下在水溶液中去碳化糖,产生甲基胺.
- 意外地,二甲基胺和三甲基胺也出现了,这表明了进一步的反应.
研究的目的:
- 为了研究从甘氨酸中自发形成甲基胺.
- 在水性介质中探索拟议的甲基胺不成比例反应.
- 阐明甲基胺转换的动力学和机制.
主要方法:
- 随着时间的推移,监测氨基产品的形成.
- 通过使用氨基缓冲器,研究反应速率作为pH值的函数.
- 研究N,N-二甲基-1,3-二胺中的甲基群迁移.
- 将硫离子作为甲基群捐赠者的反应性进行比较.
主要成果:
- 观察到甲基胺,二甲基胺和三甲基胺相互转换.
- 甲基胺不成比例的速率在和不胺氨基物种的同等度时达到顶峰.
- 在二胺中,甲基迁移遵循了第一阶动力学.
- 在甲基组转移中,三甲基硫离子的反应性明显高于四甲基离子.
结论:
- 甘氨酸脱碳化会在水中启动一连串的甲基胺不成比例反应.
- 这种依赖pH的动力学支持了一种涉及质子和不质子氨基物种的机制.
- 甲基转移反应受到甲基化剂和受体的结构的影响.
相关概念视频
Acid Halides to Amides: Aminolysis
Aminolysis is a nucleophilic acyl substitution reaction, where ammonia or amines act as nucleophiles to give the substitution product. Acid halides react with ammonia, primary amines, and secondary amines to yield primary, secondary, and tertiary amides, respectively.
In the first step of the aminolysis mechanism, the amine attacks the carbonyl carbon of the acyl chloride to form a tetrahedral intermediate. In the second step, the carbonyl group is re-formed with the elimination of a chloride...
In the first step of the aminolysis mechanism, the amine attacks the carbonyl carbon of the acyl chloride to form a tetrahedral intermediate. In the second step, the carbonyl group is re-formed with the elimination of a chloride...
Basicity of Aliphatic Amines
Amines can behave as Brønsted–Lowry bases by accepting a proton from the acid to form corresponding conjugate acids. Due to a lone pair of nonbonding electrons, aliphatic amines can also act as Lewis bases by forming a covalent bond with an electrophile.
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates higher...
To measure the basicity of amines, two conventions are generally used. The first defines Kb as the basicity constant for the deprotonation reaction of water by the amine, as presented in Figure 1. Conventionally, lower Kb indicates higher...
Preparation of Amines: Alkylation of Ammonia and Amines
Alkylation is one of the methods used to prepare amines. Direct alkylation of ammonia or a primary amine with an alkyl halide gives polyalkylated amines along with a quaternary ammonium salt through successive SN2 reactions. This process of making the quaternary salt through the direct alkylation method is called exhaustive alkylation.
Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering...
Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering...
Aldehydes and Ketones with Amines: Imine Formation Mechanism
Imine formation involves the addition of carbonyl compounds to a primary amine. It begins with the generation of carbinolamine through a series of steps involving an initial nucleophilic attack and then several proton transfer reactions. The second part includes the elimination of water, as a leaving group, to give the imine.
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Physical Properties of Amines
Amines with low molecular weight are usually gaseous at room temperature, while those with high molecular weight are liquid or solids in nature. Usually, low molecular weight amines have a rotten fish-like smell. Diamines typically have a pungent smell. For instance, cadaverine and putrescine, depicted in Figure 1, are two molecules responsible for decaying tissue.
NMR Spectroscopy Of Amines
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is broad and...


