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Chemical reactions of Alcohols, Phenols and Ethers

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  • Last Updated : 14 Mar, 2022

We’ve all had a few alcoholic beverages. Yes, it is booze. However, aside from human ingestion, it is employed in a variety of industrial uses or to create various chemicals. The same can be said for phenol and ether. These chemical molecules (alcohol, phenol, and ether) are interacted with additional chemicals to produce a new chemical. So, without further ado, let’s get to the subject. The reactions listed below will help you see these three substances in a new light.

Alcohol

Alcohols are substances that have a hydroxyl group (-OH) linked to a saturated carbon atom. Alcohol is a carbon-containing chemical molecule with a hydroxyl functional group attached. Alkenes, carbonyl compounds, alkyl halide hydrolysis, primary amines, alcohol fermentation, and ether hydrolysis are all sources of alcohol.

An aliphatic carbon’s hydrogen atom is replaced by a hydroxyl group in alcohols. As a result, there are two halves to an alcohol molecule. The first is alkylated, while the second is hydroxylated.

Alcohols are hydrocarbon derivatives with the -OH functional group, which means that a hydrogen atom has been substituted by -OH. There are three forms of alcohol: primary alcohol, secondary alcohol, and tertiary alcohol depending on the presence of hydroxyl groups in the chemical. -OH stands for the functional group of alcohol ( Hydroxyl group). Because the -OH group is connected to the carbon via a covalent connection, the nature of alcohol is predominantly covalent. Ethyl alcohol is also known as ethanol and is classified as a primary or one of the main alcohols. CnH2n + 1OH is the generic formula for alcohol.

Chemical Reactions of Alcohol

Alcohol can behave as both a nucleophile and an electrophile in reactions involving alcohol. In reactions in which the link between O and H is broken, alcohols act as nucleophiles. In reactions when the connection between C and O is disrupted, alcohols can act as electrophiles.

  • Alcohol’s reaction with the metal: Sodium ethoxide and hydrogen gas are formed when ethanol interacts with sodium metal (a base).

CH3​CH2​OH (Ethanol) +  2Na (Sodium)    →    CH3​CH2​​ONa (Sodium ethoxide)  +  H2​ (hydrogen)

  • Formation of Halides from Alcohols: The -OH group in alcohol is replaced by halogens such as chlorine or bromine.

R–OH + H–X    ⇢    R–X + H–OH

where X can be any halogen atom-like Cl, Br, etc. 

(CH3)3COH + HCl    ⇢    (CH3)3CCl + H2O

  • Reaction of Alcohols with HNO3: In this process, there is oxidation as well as gas evolution (slow but steady).

R-OH  +  HO-NO2     →     R-O-NO2

  • Dehydration of Alcohol: Primary alcohols undergo what reaction to generate alkenes, which is the most popular question asked by organic chemistry students. The dehydration reaction is the answer to this question. Alcohols are dehydrated to create alkenes when heated with a protonic acid such as conc. H2SO4 or H3PO4 at 443 K. In an acidic environment, alcohols dehydrate. According to Satyzeff’s Rule, intramolecular dehydration produces alkene, while intermolecular dehydration produces ether.

  • Hydrolysis of Alcohols: Alcohol hydrolysis is an oxidation reaction. Water serves as a catalyst in this reaction. The principal products of this hydrolysis process are aldehydes and ketones.

CH3CH2OH  +  H2O    →     CH3CHO + H2O + H2

  • Esterification of Alcohols: The creation of ester occurs when a carboxylic acid reacts with an alcohol and an acid catalyst (along with water). Fischer esterification is what it’s called. An acid or a base catalyzes esterification.

  • Haloform Reaction: In the presence of halogen and mild alkali, a chemical with the CH3CO- group (or a molecule that on oxidation gives the CH3CO – group) that is coupled with a C or H gives haloform. The haloform reaction will not affect CH3-CH2-COCH2-CH3, CH3-CO-Cl, or CH3COOH, however, the haloform reaction will affect CH3CH2OH.

  • Oxidation: The production of a carbon-oxygen double bond (C=O) with the breaking of O-H and C-H bonds occurs during the oxidation of alcohols. In oxidation reactions, this type of cleavage and bond creation takes place. Because dehydrogenation reactions include the loss of hydrogen from alcohol, they are also known as dehydrogenation reactions.

Primary Alcohol: A primary alcohol is easily oxidized to generate an aldehyde, which is followed by a carboxylic acid. The aldehyde and acid that result have the same number of carbon atoms as the parent alcohol.

Secondary Alcohol: With chromic anhydride, secondary alcohol can be quickly converted to a ketone. Under extreme conditions, the ketone might be further oxidized to produce an acid mixture. The ketone has the same amount of carbon atoms as the parent alcohol, but the acids produced have less. In the presence of an oxidizing agent, secondary alcohol is converted to the ketone.

Tertiary Alcohol: Because there is no hydrogen in the carbon-bearing hydroxyl group, tertiary alcohol is extremely difficult to oxidize (OH). When exposed to acidic oxidizing chemicals under very strong circumstances at very high temperatures, cleavage of various C-C bonds occurs, allowing for the oxidation of tertiary alcohol. They combine ketones with carboxylic acids to generate ketone-carboxylic acid combinations. The 4 number of carbon atoms in ketones and acids is lower than that of the beginning alcohols. MnO2 is an oxidizer that only oxidizes the alcohol allylic, benzylic, and propargylic.

Phenol

Ferdinand Runge, an 1834 scientist, discovered phenol. From coal tar, he was able to extract it. It’s a white, crystalline solid. Because phenol can cause chemical burns to the skin, it should be handled with caution. Phenolic acid is a different name for this substance. A six-membered aromatic ring immediately linked to a hydroxyl group is used to identify members of this species. The phenol family includes this species, which has the formula phenol. Now that you’ve learned s and the phenol formula, you’re ready to learn about the rest of the compound family.

An alkyl, alkynyl, cycloalkyl, or benzyl group could be the saturated carbon. Phenols, on the other hand, are chemicals that have a hydroxyl group connected to a benzene ring. Phenols are formed by cumene, diazonium salts, and other compounds.

Chemical Reactions of Phenol

Because a hydroxyl group linked to an aromatic ring acts as an ortho-para director, phenols are extremely reactive. As a result, phenol’s ortho and para carbons have a strong attraction for electrophilic aromatic substitution.

Williamson Synthesis: In laboratories, this is a crucial approach for making symmetrical and asymmetrical ethers. An alkyl halide reacts with sodium alkoxide to produce ether in the Williamson synthesis.

Nucleophilic Aromatic substitution

  • Formation of Ethers : 

  • Fries Rearrangement:

Oxidation to Quinones: Despite the lack of a hydrogen atom on the hydroxyl-bearing carbon, phenols are relatively simple to oxidize. The dicarbonyl molecule para-benzoquinone (also known as 1,4-benzoquinone or simply quinone) is one of the colourful products of the oxidation of phenol by chromic acid. It also has an ortho isomer. Quinones are best synthesized from these chemicals, which can be easily reduced to their dihydroxy-benzene analogues. It’s worth noting that there are no meta-quinones with similar structures. Because the redox equilibria between the dihydroxy-benzenes hydroquinone and catechol and their quinone oxidation states are so simple, gentler oxidants such as chromate (Jones reagent) are frequently used.

Electrophilic Substitution: Ortho, para – directing is significantly activated by —OH and even —O(phenoxide). Because phenols are highly reactive and prefer both poly substitution and oxidation, electrophilic mono substitution occurs in unusually mild conditions.

  • Halogenation – Because the – OH group is highly reactive, phenol is commonly polysubstituted. To avoid poly substitution, the reaction should be carried out in a nonpolar solvent such as CS2 or CCl4 and at a low temperature. When phenols are treated with bromine in the presence of a low-polarity solvent such as CHCl3 at low temperatures, mono-bromophenol is formed. Even in the absence of Lewis acids, phenols are halogenated due to the hydroxyl group’s strong activating activity. Monobromophenols are generated when phenols are treated with bromine at low temperatures in the presence of a low-polarity solvent such as CHCl3. A white precipitate of 2, 4, 6-tribromophenol forms when phenol is treated with bromine water.

  • Nitrosation: When phenols are treated with weak nitric acid, they are nitrated at 298 K, yielding a combination of ortho and para nitrophenols. On the basis of their volatility, the resulting mixture is steam distilled into ortho and para nitrophenols. Ortho nitrophenols are less volatile than para nitrophenols because they have intramolecular and intermolecular hydrogen bonds, whereas para nitrophenols only have intermolecular hydrogen bonds.

  • Kolbe’s Synthesis: The phenoxide ion is generated when phenol is exposed to sodium hydroxide. This generated phenoxide ion is extremely reactive in electrophilic substitution processes. It performs an electrophilic substitution process when exposed to a weak electrophile (carbon dioxide), resulting in Ortho-hydroxybenzoic acid. Kolbe’s response is a common term for this reaction.

  • Riemer – Tiemann Synthesis of Phenolic Aldehydes: An aldehyde group forms at the ortho position of the benzene ring when phenol is treated with chloroform in the presence of sodium hydroxide. The Reimer-Tiemann response is what it’s called.

Ether

The ether group is an organic molecule that has an oxygen atom linked to two alkyl and aryl groups.

Ethers are organic compound types that contain an ether group, which is made up of an oxygen atom linked to two aryl or alkyl groups. R – O – R′ is the general formula, where R and R′ are the aryl or alkyl groups. There are two types of ethers. A simple or symmetrical ether, for example, is one in which the alkyl groups on both sides of an oxygen atom are the same. Mixed or unsymmetrical ethers, on the other hand, are defined as ethers that are not symmetrical.

The solvent and anaesthetic diethyl ether, commonly known as “ether,” is a good example of the first group (CH3 – CH2 – O – CH2 – CH3). As common connections in lignin and carbohydrates, ethers are common in organic chemistry and even more so in biochemistry. Ethers have a structure that is similar to alcohol, and both alcohols and ethers have a structure that is similar to water. Ethers have the generic formula R-O-R, R-O-Ar, or Ar-O-Ar, with Ar denoting an aryl group and R denoting an alkyl group.

Chemical Reactions of Ether

  • Contact of ethers with air: Most aliphatic ethers progressively convert to unstable peroxides when exposed to air. The presence of peroxides is indicated by the production of red colour. When ether is shaken with an aqueous solution of ferrous ammonium sulphate and potassium thiocyanate, this colour occurs.

  • Ether Halogenation: The dark halogenation of ether produces halogenated ethers. The hydrogen atom connected to the C atom, which is directly related to the oxygen atom, is replaced by halogens.
    • Cleavage by HBr and HI: Ethers are generally non-reactive. Cleavage of the C-O bond occurs when an excess of hydrogen halide is added to the ether. Alkyl halides are produced as a result. The following is the reaction order.

Sample Questions

Question 1: What is meant by Alcohol, Phenol and Ether?

Answer:

Alcohol – Alcohols are substances that have a hydroxyl group (-OH) linked to a saturated carbon atom.

Phenol – An alkyl, alkynyl, cycloalkyl, or benzyl group could be the saturated carbon. Phenols, on the other hand, are chemicals that have a hydroxyl group connected to a benzene ring.

Ether – The ether group is an organic molecule that has an oxygen atom linked to two alkyl and aryl groups.

Question 2: How many isomers of C5H11OH will be primary alcohols?

Answer:

Four isomers of C5H11OH will be primary alcohols.

Question 3: Write Phenol’s Hydrogenation Electrophilic Substitution Reaction.

Answer: 

When phenols are treated with bromine in the presence of a low-polarity solvent such CHCl3 at low temperatures, mono-bromo phenol is formed.

Question 4: What is the distinction between ether and alcohol?

Answer:

The hydroxyl group of phenol connects directly to an aromatic ring carbon atom, whereas the hydroxyl group of alcohols attaches to a saturated carbon atom.

Question 5: Write Alcohol’s Oxidation Reactions.

Answer:

Primary Alcohol: A primary alcohol is easily oxidized to generate an aldehyde, which is followed by a carboxylic acid. The aldehyde and acid that result have the same number of carbon atoms as the parent alcohol.

Secondary Alcohol: With chromic anhydride, secondary alcohol can be quickly converted to a ketone. Under extreme conditions, the ketone might be further oxidized to produce an acid mixture. 

Tertiary Alcohol: Because there is no hydrogen in the carbon-bearing hydroxyl group, tertiary alcohol is extremely difficult to oxidize (OH). When exposed to acidic oxidizing chemicals under very strong circumstances at very high temperatures, cleavage of various C-C bonds occurs, allowing for the oxidation of tertiary alcohol. 


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