11. Alcohols, Phenols and Ethers

Alcohols, Phenols and Ethers

Class XII

Subject : Chemistry

Alcohols

Alcohols are compounds in which a hydroxyl(-OH) group attached to the saturated carbon atom.

General formula of alcohol - R-OH

The hydroxyl group is the functional group of alcohols.

Alcohols containing one hydroxyl are called Monohydric Alcohols.

Alcohols with two, three, or more hydroxyl groups are known as Dihydric Alcohols, Trihydric Alcohols, and Polyhydric Alcohols respectively.

For example,

Primary, Secondary and Tertiary Alcohols

Monohydric alcohols are classified as primary, secondary or tertiary depending upon whether the -OH group is attached to primary, secondary or a tertiary carbon.

Structure

Consider about the structure of Methyl Alcohol (CH₃OH). In methyl alcohol both oxygen and carbon are sp³ hybridized. Two of the sp³ orbitals of oxygen are completely filled and cannot take part in bond formation.

The C-O bond methyl alcohol is formed by overlap of an sp³ orbital of carbon and an sp³ orbital of oxygen. The O-H bond is formed by overlap of an sp³ orbital of oxygen and s orbital of hydrogen. The C-O-H bond angle is 105⁰. It is less than the normal tetrahedral angle. This is because the two completely filled sp³ orbitals of oxygen repel each other. This result in reduction of the bond angle.

Structure of Methyl Alcohol is given below

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4.4.2 Cyclotron Class XII.

The Cyclotron is a machine which is used to accelerate the charged particles.

This machine was invented by E.O. Lowrence and M.S Livingston. 

Construction

It has two hollow chambers of D shaped is called dees. There is some gap between the dees in which source of positive particles are kept. These dees are connected by high frequent oscillator which provides high frequent electric field between the gap of dees. This machine is placed between the two powerful electromagnetic poles.

Working Principle

Positive charged particles accelerated from D1 to D2 when D1 and D2 are positive and negative respectively. In D2 charged particles accelerated perpendicular to the magnetic field.

The schematic figure of Cyclotron is drawn below.

The charged particles move in a semi circular path perpendicular to the magnetic field.

Let the time taken to complete one revolution is T.

T = 2πm/qB
Frequency = 1/T
= qB/2πm

During the circular motion of charged particles.
mv²/r = qvB
v = qBr/m

Kinetic Energy = mv²/2
Now, putting the value of v.
Kinetic Energy = q²B²r²/2m.

Time of revolution is independent of speed of particles and radius of trajectory.

Uses of Cyclotron are as follow

1. Uses in the nuclear reactor plant
2. To implant ions into solids
3. To synthesis materials
4. To produce radio active substances in the hospital.