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(アモニウム) アミドール群における (トリアルキル) アモニウム構造がπ電子ドナー能力と熱安定性に及ぼす影響:実験的および計算的研究

  • 0Faculty of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical, and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.
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2025年8月31日

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Basicity of Aliphatic Amines 01:21

6.2K

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...

Preparation of Amines: Alkylation of Ammonia and Amines 01:30

3.7K

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...

Basicity of Aromatic Amines 01:18

7.3K

The basicity of aromatic amines is much weaker than that of aliphatic amines due to the involvement of the lone pair of electrons over the N atom in resonance with the aryl rings. Generally, the electron-donating ability of any substituents on the aryl ring of aromatic amines increases the basicity of the amine by increasing electron density, and hence the availability of lone pair on the nitrogen. On the other hand, electron-withdrawing functional groups on the aryl ring of amines decrease the...

Structure of Amines 01:19

2.7K

The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’...

Acidity of 1-Alkynes 02:42

10.0K


The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.




Ethane
(pKa = 51)


Ethene
(pKa = 44)
Basicity of Heterocyclic Aromatic Amines 01:25

6.3K

Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).

Figure 1. The comparison of the basicity of piperidine and pyridine.
This difference in basicity may be...