preparation of alcohols

Hydroxyl group attached directly to the carbon atom in the chain makes alcohol. One of the very important components of many oils, beverages, medicines, etc. alcohol preparation is a core function in the manufacturing space. 

Preparation of alcohols:-

Alcohol is a organic compound with one or more hydroxyl (–OH) compounds. The most common formula for alcohol is ROH. Alcohol is a compound containing hydroxyl (–OH) linked to the alkyl group.

Here are some formats to prepare alcohol – 

Preparation from alkenes:- 

Alkenes are acyclic hydrocarbons with at least one Carbon-to-carbon double bond and the general molecular formula is CnH2n

Methods to create alkenes are – 

a)Hydration by acid catalysed:- To form alcohols in the presence of water react alkenes. By Markovnikov’s rule in the case of unsymmetrical alkenes, the additional reaction takes place.

Example:-

Mechanism:-

The reaction involves the following three steps:-

Step 1:- By electrophilic attack of H3O+ to form carbocation from protonation of alkene. 

Step 2:- On carbocation nucleophilic attack of water.

Step 3:- to form alcohol deprotonation should take place.

1. By hydroboration-oxidation:- To give trialkyl boranes as an addiction product that reacts with an addition product by Diborane (BH3)2 in the presence of aqueous solution hydroxide oxidised to alcohols.

To the sp2 carbon the boron atom gets attached and it carries a greater number of hydrogen atoms. In a way opposite to Markovnikov’s rule by the addition of water to the alkene. In excellent productivity.

• From carbonyl compounds:-

1. From carbonyl compound reduction of aldehydes and ketone:- ketones and aldehydes are reduced by the addition of hydrogen to corresponding alcohol catalytic hydrogenation in the presence of a catalyst. Such as nickel or platinum palladium. By treating ketones or aldehydes with lithium aluminium hydride (LiAIH4) or sodium borohydrides. Whereas ketones give secondary alcohol yield aldehydes.
2. By reduction of esters and carboxylic acid:- to primary alcohols in excellent yields carboxylic acid is reduced by a strong reducing agent by lithium aluminium hydride.So, LiAIH4 is an expensive reagent used for preparing special chemicals.  By converting them to the esters by reduction of hydrogen when passed through the catalyst.

3. Grignard reagent:- By the reaction with ketones and aldehydes produced by the Grignard reagent. To the carbonyl group to form adduct the nucleophilic addition of a Grignard reagent.

Hydrolysis of the adduct and alcohol.

Using different ketones and aldehydes:-

example

With methanal with other tertiary alcohols with ketones, secondary alcohol produces many alcohols.

Preparation of phenols:-

From coal tar in the early nineteenth was first isolated known as carbolic acid and phenol. So carbolic acid is commercially produced. From benzene derivatives phenols are prepared by any of the methods:-

1. From haloarenes:-at 623k and 320 atmospheric pressure with NaOH when chlorobenzene is fused by the acidification of sodium phenoxide so produced. 
2. From benzene sulphonic acid:- With oleum and benzene sulphonic acid so formed is converted with molten sodium hydroxide benzene sulfonated given phenol acidification of the sodium.
3. From Diazonium salt:- At 273-278k with nitrous acid (NaNO2 + HCl)  by treating an aromatic primary amine is formed by a Diazonium salt. By treating dilute acids to phenols by warming them with water salts are Diazonium salts.
4. For cumene:- From the hydrocarbon cumene phenol is manufactured. To cumene in the presence of air cumene is oxidised. By treating it with dilute acid it is converted to acetone and phenol. By product in this reaction is acetone obtained in enormous quantities.

Physical properties:-  

A hydroxyl and alkyl group combine to form phenols and alcohols. The properties of alcohols are due to the hydroxyl group and phenols properties. Simply modify these properties the nature aryl groups and an alkyl group. Simply modify these properties of the nature of aryl groups and alkyl groups. 

Boiling points:-  Increase in the number with alcohol and phenols with an increase in several carbon bond atoms in van der Waals forces.  With the increase in chain branching, the boiling point decreases; there is an indirect relation between carbon chain numbers and boiling point. Due to the presence of intermolecular hydrogen bonding that lacks hydrocarbons and ethers. 

For example:- 

CH4(296°C), CH3Cl (249°C)

Solubility:- 

Due to the formation of hydrogen bonds with water molecules, I water solubility of phenol and alcohols. Increase in size of aryl and alkyl; alcohol due to which solubility decreases.

For example:- Alcohol and its Solubility.

N-Butyl alcohol                 7.9

N-Pentyl alcohols             2.3

Chemical reaction:- 

Versatile compounds are alcohols they react as electrophiles and nucleophiles both and between O-H is detached when alcohols react with nucleophiles.

Alcohols as nucleophiles:-

Protonated alcohols react with the matter C-O bond is broken when they react with electrophiles.

As electrophiles:- Observing the cleavage of the bond of C-O and O-H the reaction can be divided into two groups of alcohols and phenols.

A)Cleavage of O-H bond involving in the reaction:-

1. Acidity of phenols and alcohols:-i). Reaction with metals:- with active metal such as aluminium potassium sodium from alcohols and phenols to yield corresponding alkoxides and hydrogen.

With aqueous sodium to form sodium phenoxide reacts with phenols.

They are acidic even though these are bronsted acids that mean they donate protons and provide a base of strong nature.

ii). Alcohols of acidic:-

To decrease the polarity of the O-H bond an electron releasing group increases density on oxygen tending properties due to the polar nature of the O-H bond.

 Note:- Even alcohols are acidic less than water. with an alkoxide a better proton donor than alcohols. A better proton acceptor than hydroxide ions that proves alkoxides are stronger bases.

Alcohols as well act as bronsted bases. due to unshared pairs of oxygen that make protons as acceptors.

iii) Phenols acidity:- Sodium hydroxide indicates the reaction of phenol and its acidic nature. The hydroxyl group as an electron-withdrawing group is directly attached to the sp2 hybridised carbon of benzene reaction to act as withdrawing electron group. With sodium hydroxide the charge distribution in phenol as depicted in resonance structure causes oxygen to become positive in the O-H group. An aromatic ring is attached to an alkyl group. The ionisation of phenol and alcohol takes place as follows:-

for example:-

Electron density decreases on oxygen –OH is attached due to higher electronegativity of sp2 hybridised carbon on the oxygen of phenol decrease in electron density. In the end, there is an increase in ionisation of phenols than alcohols, the delocalised charge is negative.

2. Esterification:- with carboxylic acid, acid chlorides and acid anhydrides react alcohols and phenol to form esters.
   Out in the presence of a small amount of concentrated sulphuric acid the reaction with an acid anhydride and carboxylic acid. Water is removed when the reaction is reversible., as soon as it is formed. To neutralise HCl out in the presence of a base formed during the reaction. In phenols and alcohols is known as acetylation.

4. Oxidation:- With cleavage of an O-H and C-H bonds the formation of a carbon double bond. In oxidation reactions, such cleavage and formation of bonds occur known as dehydrogenation reactions. A primary alcohol is oxidised to aldehyde which later turns into a carboxylic acid.