Reduction reaction is that a substance (molecule, atom or ion) obtains electrons orElectron pairNear reaction.A completechemical reactionMedium, reduction reaction andoxidation reaction Generally, they exist at the same time.
Chinese name
Reduction reaction
Foreign name
Reduction Reaction
Concept
Get the reaction of electrons or electron pairs closer
Essentially, electron transfer (or shift) occurs, but it is not limited to different elements.
Most inorganicMetathesis reactionThey are not redox reactions, because the ions in these double decomposition reactions exchange with each other, there is no electron transfer, and the oxidation number of each element does not change
In addition, it should be noted that chemical reactions involving elements are not necessarily redox reactions, such as the formation of ozone by oxygen (only in the middle school stage, it can be considered that in fact, due to the electron shift, they are still redox reactions).
concept
The essence of the reaction is the change of the oxidation number, that is, the transfer of electrons.Oxidation numberThe half reaction of electron loss is oxidation reaction;When the oxidation number decreases, the reaction to obtain electrons is a reduction reaction.The substance with increased oxidation number will be oxidized by reducing the other, so it is calledreducing agent, the product is calledOxidation product；The substance with reduced oxidation number oxidizes the other and is reduced itself, so it is called oxidant, and its product is calledReduction product。That is:
Generally speakingReducibilityWeaker than reducing agentOxidizabilityIt is weaker than oxidant, which is called "strong reductant makes weak reductant, strong oxidant makes weak oxidant".
Primary battery
Announce
edit
every lastRedox reactionCan be made into a primary battery.The anode where the oxidation reaction takes place is the negative pole of the external circuit;One pole of the reduction reaction is the cathode, that is, the positive pole of the external circuit.Between the two electrodesPotential difference（electrochemistryUsually calledemf）So the reaction can proceed and can be used to do work.
oxidation reaction
Announce
edit
Oxidation reaction refers to the combination of metal or nonmetal with oxygenoxideThe oxidation number of another element always increases in such reactions.Reduction reaction refers to the reaction in which metals are extracted from their compoundsOxidation numberAlways lower.
Another example is the reaction of industrial ironmaking:
BoraneAnd carbon carbon unsaturated bondAlkyl groupThe reaction of borane is called borohydride reaction.The formed alkyl borane is addedacid hydrolysisThe carbon boron bond is broken to obtain saturated hydrocarbon, thus reducing the unsaturated bond.
stayacetic acidWhen platinum is used as catalyst,SubstituentThe activity of ArOH>ArNHtwo＞ArH＞ArCOOH＞ArCHthree。Different catalysts have different activity sequencesRuthenium catalystIt can be hydrogenated at lower temperature and pressure, while palladium requires higher temperature and pressure.
Aldehydes and ketones can be reduced to alcohols by various methods. Metal hydride reduction and catalytic hydrogenation reduction are the most widely used. In addition, alcohol aluminum reducing agents, active metal reducing agents, and other new reagents are also widely used.
Reduction to hydrocarbons
Common methods include: under strong acid conditionsZinc amalgamdirect reduction Is hydrocarbon (Clemmensen reaction);Under strong alkaline conditions, it first reacts with hydrazine to form hydrazone, and then decomposes into hydrocarbon (Wolff Huang Minglong reaction);Catalytic hydrogenation reduction andmetal hydride Restore.
In acid conditions, useZinc amalgamOr zinc powder reducing aldehyde groupKeto groupMethyl ormethyleneClemmensen reaction.It is often used for the reduction of aromatic fatty ketones, and the reaction is easy to carry out andyield Higher.
2. Wolff Huang Minglong reaction
Aldehydes, ketones andHydrazine hydrateCondensate to hydrazone, and then release nitrogen to decompose into methyl ormethyleneThe reaction is called Wolff Huang Minglong reaction.It can be expressed by the following general formula.
It is obtained by addition of carbonyl and amine through Schiff base intermediatehydroxylamine, followed by dehydrationImineAnd finally reduced to amine compounds.
2. Leuckart reaction
stayformic acidThe reductive amination of carbonyl compounds with ammonia and amine in the presence of carbonyl compounds and their derivatives.
Reduction of carboxylic acids and their derivatives
The acyl halides react under appropriate conditions and are selectively reduced to aldehydes by catalytic hydrogenation or metal hydride. This reaction is called Rosenmund reaction.
Common methods for reducing nitro compounds include active metal reduction, sulfide reduction, catalytic hydrogenation, complex hydride reduction andCOSelective restore.
Hydrogenolysis reaction - the reaction in which the carbon hetero bond breaks in the reduction reaction and hydrogen replaces the leaving heteroatoms or groups to generate hydrocarbons.
