Analyze the density and spatial effect of the central atom electron cloud to judge the alkalinity.

Using the acidity and alkalinity of organic matter, compounds can be separated in organic chemistry, and the differences in reactivity of substances can be compared.

Answer supplement

1, the acidity and alkalinity can be determined by analyzing the electronic effect (induced effect, * * * yoke effect).

Inductive effect affects the acidity and alkalinity of substances: the greater the ability of substances to give protons, the stronger the acidity. The ability to give protons depends largely on the ability of the substituents around the molecule to disperse charges when they lose protons to form negative ions. The more dispersed the charge of the formed carboanion is, the stronger and more stable the ability to generate protons is. Therefore, any structural factor that disperses charge can improve the stability of negative carbon ions, and vice versa. Generally speaking, electron-withdrawing substituents can improve the acidity of organic compounds, while electron-donating substituents can reduce their acidity.

* * * Yoke effect will also affect the acidity and alkalinity. In the * * * yoke system, electron delocalization expands the range of electron motion and makes the system stable. The carbonyl group in carbonyl compounds is a polar double bond, and its α -hydrogen has certain acidity due to the induced effect and the * * * yoke effect. However, the acidity of α -hydrogen is different in different chemical environments.

2. For organic compounds with different structures, we can compare the acidity and alkalinity of products through some reactions.

Some compounds are quite different in structure, so it is difficult to determine their acid-base relationship through the spatial effect of electronic effect, such as sodium acetylene, sodium amino, sodium hydroxide and so on. These three compounds are all bases, and their alkalinity order can't be known at a glance, but we can compare the existing reactions in the literature, so that we can clearly see the acidity and alkalinity of organic compounds.

HC=CH +NaNH2-HC= CNa+H3。

HC = = CNA+ho-HC = = methane+sodium hydroxide

It is not difficult to see from the above that according to the law that weak acid is obtained by the reaction between strong base and weak acid, the alkalinity of sodium amino is stronger than that of sodium acetylene, while that of sodium acetylene is stronger than that of sodium hydroxide. On the other hand, it also shows that the acidity of acetylene is stronger than that of ammonia, while the acidity of acetylene is weaker than that of water. Knowing this, it is not difficult for us to understand that reactions involving carbanions such as sodium acetylene must often be carried out under anhydrous conditions. It is also an effective method to determine the acid-base relationship between chemicals through some reactions.

In a word, judging the acidity and alkalinity of organic matter can be considered from the following aspects: for organic matter with similar structure, its acidity and alkalinity can be compared by electronic effect (including induced effect and * * * yoke effect); For organic compounds with different structures, the acidity and alkalinity should be judged according to the related reactions in the literature.