The double bond reacts with the acidic or alkaline aqueous solution of KMNO4, causing KMNO4 to fade.

In neutral or alkaline media, dark brown MnO2 precipitates.

The double bond causes the reddish-brown color of bromine to recede

The double bond reacts with cold concentrated sulfuric acid to make the mixture homogeneous

Unsaturated bonds make potassium permanganate fade away from its purple color

Terminal alkynes release carbon dioxide

The unsaturated bond causes the red-brown color of bromine water to fade away

The terminal alkyne reacts with it to produce silver acetylene precipitation (white)

The terminal alkyne reacts with it to form a copper alkyne precipitate (brown-red)

Cyclopropane and its hydrocarbon derivatives react with bromine in carbon tetrachloride solution to cause the reddish-brown color of bromine to recede

Conjugated diene and maleic anhydride undergo diene synthesis reaction to precipitate solid

Benzene, its homologs, and halogenated aromatic hydrocarbons turn orange-red after reaction

Naphthalene turns blue after reaction

The reaction between phenanthrene and biphenyl turns red

Anthracene turns green after reaction

Alkylbenzenes with a-H can discolor potassium permanganate

The reaction between benzene and its alkylbenzene and fuming sulfuric acid makes the reaction solution homogeneous.

Halogenated hydrocarbons (except fluoroalkyl) with only one halogen attached to each carbon can react with the solution to generate AgCl white precipitate, AgBr light yellow precipitate, and AgI yellow precipitate.

Ethylene halogens and alkanes with two or more halogens attached to the same carbon do not have this reaction.

Allyl halogen, 3>2>1> vinyl halogen

RI>RBr>RCl

Allyl benzyl and tertiary halogenated hydrocarbons precipitate immediately at room temperature, primary and secondary halogenated hydrocarbons precipitate when heated, and vinyl-benzene halogenated hydrocarbons do not precipitate when heated.

Alkanes bromides and chlorides are treated with this reagent to form NaBr or NaCl precipitates.

Allyl halogen, benzyl halogen>1>2>3>ethylene type

RBr>RCl

CH3OH>1OH>2OH>3OH

The increase in the hydrocarbyl part of the molecule reduces the activity

Used to distinguish C3-C8 alcohols from non-alcohols. Alcohols below C3 should not be detected by this method.

Reaction speed: allyl alcohol, benzyl alcohol = 3 alcohols > 2 alcohols > 1 alcohols

3OH reacts the fastest and immediately generates chlorinated hydrocarbons that are insoluble in water. They appear turbid and stratified when placed.

It takes several minutes for 2OH to become turbid.

1OH will not cause turbidity in a short period of time

Only suitable for alcohols below C6

1OH and 2OH can be oxidized by this reagent and change from orange-red to green.

Tertiary alcohols without a-H should not show any reaction within 2s, and changes after 2s can be ignored.

Binary or polyvalent o-hydroxyl alcohols, sugars, o-hydroxylamines, a-amino and a-hydroxyketone aldehydes and a-diketones can be oxidized, and then react with AgNO3 to form AgIO3 precipitation (white)

Distinguish between vicinal diols and related compounds

Most phenols react with it and turn blue, purple or green

Most nitrophenols, meta- and para-hydroxybenzoic acids are non-color reactive

Some phenols, a-naphthol, b-naphthol, etc. also have no color reaction with them.

If an ethanol solution is used, a positive result will be displayed

Phenols discolor bromine water

Phenol reacts with bromine water to form white solid tribromophenol

The carbonyl group in aldehydes and ketones reacts with this reagent to form yellow, orange, orangish-red 2,4-dinitrophenylhydrazone precipitates.

Aldehydes, cyclic ketones below C8, and aliphatic methyl ketones can react with the saturated solution to produce white crystals

Compounds with a specific structure react with I2/NaOH to generate CHI3 crystals (yellow)

Fatty aldehydes can reduce Fehling's reagent and precipitate yellow to red precipitates.

Fatty aldehydes reduce this reagent to form a yellow to red precipitate.

The aldehyde encounters Tollen's reagent and forms a silver mirror on the wall of the vessel. also known as silver mirror test

The aldehydes react with this reagent to produce a purple-red color, and the one that does not fade after adding sulfuric acid is formaldehyde.

Bubbles are produced

Bubbles are produced and the clear limewater becomes turbid.

pH test paper is acidic in color

When distilled water is added to the acid halide, it is hydrolyzed immediately, exothermic and hydrogen halide is released. When silver nitrate solution is added, it precipitates again to form

Acid anhydride is added dropwise to distilled water. It sinks first and then hydrolyzes after a while.

Add distilled water to esters and amides at room temperature and separate into layers without any obvious phenomenon.

Acid halides, acid anhydrides, esters, amides react with hydroxylamine hydrochloride and are treated with FeCl3 to turn red to purple.

N-substituted amides are unreactive

If it is an aromatic amide, NH2OH·HCl may not be used, but H2O2 may be used to oxidize hydroxamic acid.

Any nitro group containing a-H can react

Tertiary nitroalkane does not react

Primary amines produce red and secondary amines produce blue.

Dissolve aromatic nitro compounds in ethanol and acetone, and add 10%-20% NaOH solution

Mononitrobenzene does not produce color

The benzene ring substituted by two nitro groups has a blue-purple color

If there are amino groups, substituted amino groups or hydroxyl groups in the molecule, it will inhibit the formation of the characteristic red and purple colors.

Primary amines give off nitrogen gas

Secondary amines produce yellow oil or solid

Tertiary amines form green crystals

Primary amines form white solids, which are soluble in NaOH

Secondary amines form white solids that are insoluble in NaOH.

Tertiary amines are unreactive (soluble in acids)

Usually produces a dark blue to blue-green solution with divalent copper

Furan reacts with HCl-impregnated pine wood chips and turns green

Pyrrole reacts with HCl-infiltrated pine wood chips to produce red color

Thiophene indigo turns blue under concentrated sulfuric acid

Sugar with a specific structure can react with excess phenylhydrazine when heated in a water bath to form yellow crystals--

Alcohol part

Tollen's reagent

Feeling reagent

Benedict's reagent method

(1) Resorcinol method

(2) Bromine water method

Both sugar substances and Molich reagent develop color, and a purple ring appears.

Starch solution I2-KI generates blue, becomes colorless when heated, and returns to blue when cooled

Any substance containing free amino groups can react with ninhydrin to develop a blue-purple color

Proline, hydroxyproline, and o-, m-, and p-aminobenzoic acids all produce yellow color

Ammonium salts produce blue-violet, and some amines (aniline) produce orange-red

Amino acids (tyrosine) and proteins (tyrosine groups) containing phenolic hydroxyl groups react with Millon to form a brick-red precipitate.

Amino acids (tyrosine, tryptophan, phenylalanine) and proteins containing benzene rings will produce yellow precipitate or yellow solution when boiled with concentrated nitric acid.

For polypeptides and proteins with two or more special structures, add 20% NaOH aqueous solution, then add dilute CuSO4, boil, and a purple-red precipitate will form.

Alpha-amino acids containing free amino groups, primary amines, and amides can react with nitrous acid to release nitrogen gas.