What is the functional group?

There are interactions among groups in organic molecules, including the influence of functional groups on hydrocarbon groups, the influence of hydrocarbon groups on functional groups, and the interactions among functional groups in substances containing multiple functional groups.
① Alcohols, phenols and carboxylic acids contain hydroxyl groups in their molecules, so they can react with sodium to release hydrogen, but due to the different groups connected, there are differences in acidity.
R-OH is neutral and cannot react with NaOH and Na2CO3; the hydroxyl group directly connected to the benzene ring becomes a phenolic hydroxyl group, and the hydroxyl group not directly connected to the benzene ring becomes an alcoholic hydroxyl group.
C6H5-OH is very weakly acidic, weaker than carbonic acid, but stronger than HCO3-(bicarbonate). Can not make the indicator change color, can react with NaOH. Phenol can also react with sodium carbonate to generate sodium phenolate and sodium bicarbonate;
R-COOH is weakly acidic, has the property of acid, and can react with NaOH and Na2CO3.
Obviously, in carboxylic acids, the influence of the carbonyl group in the carboxyl group makes the hydrogen in the hydroxyl group easy to ionize.
② Both aldehydes and ketones have carbonyl groups (>C=O), but the carbonyl carbon atoms in aldehydes are connected to a hydrogen atom, and the carbonyl carbon atoms in ketones are connected to hydrocarbon groups, so the former has reducibility, and the latter is relatively stable, not weak oxidized by oxidants.
③ Atomic groups in the same molecule also affect each other. Like phenol, -OH makes the benzene ring easily substituted (activated), and phenyl makes -OH acidic (ie, ionizes H+). In fructose, the polyhydroxyl group affects the carbonyl group, and the silver mirror reaction can occur.
As can be seen from the above, we can not only determine the chemical properties of organic matter by the functional groups contained in the organic matter, but also judge the functional groups contained in it by the chemical properties of the substance. For example, glucose can undergo silver mirror reaction, hydrogenated and reduced to hexavalent alcohol, and it can be known that it has an aldehyde group; it can be esterified with acid to generate glucose pentaacetate, indicating that it has five hydroxyl groups, so it is a polyhydroxy aldehyde.
Organic chemistry reactions take place primarily on functional groups, so pay attention to what bonds the reactions take place on in order to write chemical equations correctly.
For example, the hydrogenation of aldehyde occurs on the carbon-oxygen bond of the aldehyde group, and the oxidation occurs on the carbon-hydrogen bond of the aldehyde group; the substitution of halogenated hydrocarbon occurs on the carbon-halogen bond, and the elimination of carbon occurs on the carbon-halogen bond and adjacent carbon atoms. On the hydrogen bond; the esterification of alcohol is the breaking of the O-H bond in the hydroxyl group, and the substitution is the breaking of the C-O bond; the addition polymerization is a carbon-carbon double bond (>C=C<) (not necessarily an olefin) The unique reaction of the compound is that during polymerization, the groups on the carbon of the double bond are thrown up and down, and one bond in the double bond is opened and connected hand in hand.