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Alcohol & Ether

Alcohol- Alcohols are chemical compounds that have an alkyl group or hydrocarbon chain bonded to the carbon atom by one, two, or more hydroxyl groups (OH).

Classification of Alcohol- Alcohols are classified as monohydric, dihydric, trihydric, or polyhydric based on the fact that they contain one, two, three, or more than three hydroxyl groups.

Monohydric alcohols are further categorized as follows:

  • Hydroxyl group is connected to an alkyl group having sp3 hybridized carbon atoms in compounds with Csp3-OH bond. It is further divided into three types: primary, secondary, and tertiary alcohols.
  • Allylic Alcohols- In close proximity to the carbon-carbon double bond, a hydroxyl group is connected to the sp3 hybridized carbon atom.
  • Benzylic Alcohols: The hydroxyl group is joined to the sp3 hybridized carbon atom of the aromatic ring.
  • The hydroxyl group is connected to the sp2 hybridized carbon atom in compounds with a Csp2-OH bond. They are also referred to as vinylic alcohols.

Structure- C and O sp3 hybridized orbitals are linked by a bond.

  • Bond Angle- The C-O-H bond angle is 108.9 °, which is smaller than the tetrahedral value of 109 °-28 ‘. It results from the attraction of oxygen electron pairs.
  • Bond Length- The C-O bond in methanol has a length of 142 pm.

Preparation- Alcohol can be made by using acid-catalyzed hydration of alkenes, by hydroboration oxidation reaction of alkene, by Carbonyl Compounds, by reduction of carboxylic acids & esters and by Grignard reagent.

Physical Property- Van der Waal forces rise with the number of carbon atoms, raising the boiling point of alcohols.  Because alcohols create hydrogen bonds with water molecules, they are soluble in water.

Chemical Reaction- Alcohol (O-H bond cleavage) reacts as a nucleophile in the following reactions: Alcohol reacts with metal to generate alkoxide. On the formation of esters by the interaction of alcohols with carboxylic acids, acetic anhydride, and acid chloride. Reactions involving C-O bond cleavage: Alkyl halide is formed when alcohol combines with HX. Oxidation produces aldehyde and ketone. Alcohols are dehydrogenated when heated with Cu at 573 Kelvin.

Ether- Ethers are chemical molecules with an oxygen split between two alkyl groups. They are represented by the formula R-O-R’, with R’s representing alkyl groups. These chemicals are found in dyes, fragrances, oils, waxes, and uses in industry.

Ethers are classified into two types-

  • Symmetrical- O is attached to the same groups.
  • Unsymmetrical- O is attached to various groups.

Structure-

  • Bond Angle- The C-O-C bond has an angle of 111.7 degrees (Methoxymethane).
  • Bond Length- The C-O bond has a length of 141 pm, which is about the same as alcohol.
  • Because of the repulsion between the two classes of R (bulky), it is more than tetrahedral.

Preparation- When primary alcohols are treated with protic acids (H2SO4, H3PO4), the nucleophilic bimolecular reaction yields ether. This reaction is temperature dependent, with alkene being a major product at 443 K and ether being a major product at 413 K. When alcohol is 2° or 3°, the elimination process competes with SN1, resulting in alkene as the major product. Ether can also be made by William synthesis.

Physical Properties- Ether miscibility is similar to alcohol and greater than alkane of the same molecular mass due to the establishment of a hydrogen bond with water and O of ether. Because of intermolecular hydrogen bonding, the boiling point is lower than that of alcohols.

Chemical Reaction- Chemical reactions in ether include the absence of the O-H link in ethers, reactions involving the cleavage of the CO bond, electrophilic substitution reactions, and the Friedel Crafts reaction.

Conclusion-

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