High school chemical organic reagent identification, high school test organic matter existence of co

Bromine is the only non-metallic element that is liquid at room temperature and is one of the six elements on the periodic table that are liquid at or near room temperature. The melting point of bromine is °C, while the boiling point is °C. The elemental element in its form is a diatomic molecule :

br 2。It is a viscous, flowable, reddish-brown liquid that volatilizes easily at standard temperatures and pressures, forming a red vapor (similar in color to nitrogen dioxide) and has a foul odor similar to that of chlorine. Bromine is a halogen that is less active than chlorine but greater than iodine.

Bromine is slightly soluble in water, but has good solubility to carbon disulfide, organic alcohols (like methanol) and organic acids.

Bromine water, a mixture of bromine elemental matter and water. Bromine elemental is soluble in water, and more than 80% of bromine will react with water to form hydrobromic acid and hypobromic acid, but there will still be a small amount of bromine elemental dissolved in water, so bromine water is orange-yellow. The new bromine water can be regarded as an aqueous solution of bromine, which undergoes a chemical reaction related to bromine, but the bromine molecules in the bromine water for a long time will also decompose, and the bromine water will gradually fade.

Stored bromine water contains only hydrobromic acid. Hypobromic acid will decompose into hydrobromic acid and oxygen upon exposure to light.

The chemical formula of potassium permanganate is KMNO7, where manganese shows 7 valence, which is its highest oxidation valence state, so potassium permanganate solution has strong oxidation. Generally, when preparing potassium permanganate solution, a small amount of sulfuric acid will be added, otherwise the hydroxide ions in the solution will be manganese precipitate during long-term storage.

Benzene (C6H6) is a colorless, sweet-smelling transparent liquid at room temperature with a strong aromatic odor. Benzene is flammable, toxic, and a carcinogen. Benzene is a hydrocarbon and the simplest aromatic hydrocarbon.

It is insoluble in water, soluble in organic solvents, and can also be used as an organic solvent in itself. The ring system that benzene has is called benzene ring, which is the simplest aromatic ring. The structure of a benzene molecule after removing a hydrogen is called phenyl group, which is denoted by pH.

Hence benzene can also be expressed as PHH.

Ethylene, molecular formula: C2H4;Structure: ch 2=ch 2;Minimalist:

ch 2。Normally, ethylene is a colorless and slightly odorous gas with a density of slightly less dense than air, insoluble in water, and easily soluble in organic solvents such as carbon tetrachloride.

Appearance and properties: colorless gas, slightly odorous with hydrocarbons. A small amount of ethylene has a faint sweetness.

Toluene, appearance and properties: colorless transparent liquid, with aromatic odor similar to benzene.

Melting point ( ) relative density (water = 1):

Boiling point ( ) solubility: insoluble in water, miscible in benzene, alcohol, ether and other organic solvents.

Chemical properties. The chemical properties are reactive, similar to benzene. Oxidation, sulfonation, nitration and disproportionation reactions can be performed, as well as side-chain chlorination. Toluene can be oxidized to benzoic acid.

I've been collecting it for a long time, and I really want it!

Ethylene is able to make the acid potassium permanganate bromine water fade and is a chemical change.

Benzene cannot discolor acidic potassium permanganate but can discolor bromine water and extract physical changes.

Toluene can be oxidized by acidic potassium permanganate to formic acid, so it can fade acidic potassium permanganate.

Bromine is a pure substance, bromine water is a mixture, and acidic potassium permanganate is a mixed salt solution.

The essence of testing organic matter is to inspect the functional group.

1. Unsaturated bonds (carbon-carbon double bonds, triple bonds): bromine water, carbon tetrachloride solution of bromine, acidic potassium permanganate; Phenomenon: Fading.

2. Alcohol hydroxyl group: acidic potassium permanganate solution; Phenomenon: Discoloration (Condition: With -Hydrogen).

3. Phenolic hydroxyl group: ferric chloride solution; Phenomenon: Color reaction (different phenols have different colors, but high school seems to only require that phenol is purple and late).

4. Aldehyde group: Feilin reagent or silver ammonia solution; Phenomenon: brick-red precipitation or silver mirror.

5. Carboxyl group: There seems to be no special method to test the carboxyl group, if required, use acid-base indicator, stone scatter imitation compass and the like.

6. Halogen atoms: after coheating with sodium hydroxide aqueous solution, silver nitrate solution is added after acidification with dilute nitric acid, and precipitation (chlorine-silver chloride-white precipitation; bromine-silver bromide-yellowish precipitate; Iodine-silver iodide - yellow precipitate).

7. Others, such as benzene homologues, can be tested with acidic potassium permanganate, and the phenomenon is also fading.

Some methods, such as fading acidic potassium permanganate, cannot determine what functional groups there are, so it is recommended to learn organic can not remember the test method like inorganic, but should summarize more for common question types (inference questions and synthetic questions, organic two types of key question types), such as which functional groups can fade acid potassium permanganate, which functional groups can fade bromine water, I don't know if the above content can help you

Keep in mind some common identification methods and phenomena, such as:

Carboxyl: purple litmus solution, sodium bicarbonate solution, copper hydroxide, etc.

Phenols: ferric chloride solution, bromine water, etc.

Aldehyde group, glucose: silver mirror reaction, copper hydroxide suspension, etc.

Starch: iodine water, etc.

Hydroxyl group: sodium, etc., polyhydroxy group: new copper hydroxide suspension, etc.

Unsaturated bonds (double, terri): bromine water or carbon tetrachloride solution of bromine, etc.

Phenol is added to FeCl3

The solution is purple;

Glycerol is added to the freshly prepared copper hydroxide solution to produce a blue solution; fructose plus silver ammonium solution is produced by silver mirror, and acetone plus 2,4-dinitrophenylhydrazine has a yellow precipitate; The remaining few were added to Lucas reagent, and the first to appear turbid was isopropanol; Then the remaining undetected potassium permanganate solution was added, and the discolored ethanol was added; The remaining 2 samples were added to the hydrochloric acid solution, heated, and the gas released was urea, and the remaining was triethyl.

Option C analysis: The commonly used reagents for the identification of organic matter are: water, bromine water, acidic potassium permanganate, newly prepared Cu(OH)2, FeCl3 solution, etc.

1) Consider water (2) Special reactions (3) Color reactions.

A with water, ethanol and water miscibility, toluene and nitrobenzene add the same water will stratify the upper layer less toluene on the contrary nitrobenzene (toluene density is smaller than water, nitrobenzene density is greater than water).

b With concentrated bromine water, phenol can produce white precipitate (tribromophenol) with concentrated bromine water, hexene can fade it, and the upper layer of orange-red stratification is benzene.

Item C cannot be identified with one reagent (potassium permanganate can only identify toluene).

D was identified with a new Cu(OH)2 suspension. Formic acid and acetic acid can dissolve Cu(OH)2, and only formic acid will produce a red precipitate (there is an aldehyde group in formic acid) after heating at the same time; Acetaldehyde does not react with Cu(OH)2 at room temperature, and is heated to form a red precipitate.

Hope it helps.

When I choose CA, I use water. Ethanol is miscible with water. Toluene is less dense than water. Float on water. Nitrobenzene is denser than water and sinks to the bottom.

b with bromine water. Benzene does not react. Phenol produces a white tribromophenol precipitate.

Hexene fades bromine water with copper hydroxide. Formic acid can produce a red precipitate with its water bath, which is then dissolved. Acetaldehyde produces only a red precipitate.

Acetic acid makes the blue flocculent precipitate of copper hydroxide disappear.

If you have any questions, please ask.

It's so difficult, if it's me, choose C, for the following reasons:

a, needless to say, the water can look at the layering, toluene on the top, nitrobenzene on the bottom;

B, I think it can be identified with bromine water, benzene and bromine water extraction, the upper layer will have a dark color, the lower layer is water, phenol and bromine react to form tribromophenol, white precipitate. Hexene reacts with bromine, but it should be a colorless liquid;

C, stumped me.

D, the first choice of Feilin reagent (silver ammonia solution), can also be identified according to the nature of the acid, first of all, acetaldehyde does not react, but there is a difference in the speed of the reaction between the two, this is a bit far-fetched, but from an experimental point of view, the concentration is appropriate, or obvious.

Therefore, C. To digress, this kind of organic identification question is generally identified by using solubility, characteristic reaction, density, and degree of reaction, c This option, there are too many similarities between the three, the density is less than water, insoluble in water, and there are similar functional groups A reagent, which is really not common in high school. If you really want to say it, NBS is barely okay, it's out of class, A B D has normal reagents, so don't consider C! Hope you are satisfied.

b.BR can experiment with different results.