- Alkyl halides though polar are immiscible with water?
Ans: Alkyl halides are polar but are insoluble in water because energy required to break the intermolecular H-bonding among water molecules is much higher than energy released by water halide interaction.
- Why the dipole moment of chlorobenzene is lower than cyclo. Hexane.
Ans In chlorobenzene C-Cl bond has some double bond character so its bond length is smaller. Hence dipole moment is smaller than cyclohexane chloride which has a longer C-Cl single bond.
- Solubility of Alcohols
Solubility of alcohols is water is due to their ability to form hydrogen bond with water molecules. The solubility decreases with increase in size of alkyl groups and solubility increase with increase in branching the order is 10<20<30.
- Boiling Point of Alcohols
The boiling point of alcohol increases with increase in No. of carbon atoms as van der wall forces increases and boiling point decreases with increase in branching of carbon chain due to decrease in van der wall forces with decrease in surface area and the order is 10<20<30.
- Acidity of Alcohols
The acid strength of alcohols decrease in order
10>20>30.
- Solubility of ethers
Ethers are soluble in water to certain extent due to H-bonding.
Solubility decrease with increase in mol. Mass
Ethers are fairly soluble in all organic solvents such as chloroform, alcohol, benzene etc.
- Solubility of phenols
Like alcohols, phenols are soluble in water due the formation of H-bonding with water.
Phenols are less soluble than alcohols due to large hydrocarbon (benzene ring)
Phenols are soluble in alcohols, ethers and also in NaOH.
- Boiling Point
Much higher than corresponding hydrocarbons and haloarenes due to inter molecular H-bonding.
Boiling point of Aldehydes and Ketones
The Boiling Point of aldehydes and ketones are higher than hydrocarbons and ethers of comparable molecular mass due to weak dipole-dipole interaction.
Their boiling point are lower than those of alcohols of similar molecular mass due to absence of intermolecular H-bond.
Among isomeric aldehydes and ketones, ketones have slightly higher boiling point due to the presence of two electron releasing group which make carbonyl group more polar.
- Solubility of Carboxylic Acid
Simple aliphatic carboxylic acids having upto C4 atoms are miscible in water due to formation of H-bond with water.
The solubility decrease with increasing No. of carbon atoms. Higher carboxylic acids are practically insoluble in water due to the increased hydrophobic interaction of hydrocarbon part.
Benzoic acid the simplest aromatic carboxylic acid is nearly insoluble in cold water.
- Boiling point of Carboxylic acid
Carboxylic acids have higher boiling point than aldehydes, ketones and even of comparable molecular mass due to more extensive association of their molecules through intermolecular H-bonding. The H-bonds are not broken completely even in their vapour phase.
- Boiling point and solubility of Amines
10 and 20 amines have higher boiling point than other organic compounds due to H-bonding.
Primary and Secondary amines are soluble in water due to H-bonding
Amines are basic in nature due to the presence of lone pair of electron on nitrogen atom.
Aliphatic amines are stronger bases than ammonia due to +I effect of alkyl group present in Amines.
Aromatic amines are weaker bases than ammonia due to -I effect of aryl. Group.
Besides inductive effect there are effects like steric effect, solvation effect, resonance effect which affect the basic strength of amines.
In gaseous phase, the order of basicity
30 amines > 20 amines >30 amines >NH3
In aqueous phase, despite of inductive effect, solvation effect and steric hindrance also plays an important rule. Thus, the order of basicity of amines is
(C2H5)2NH >(C2H5)3N > C2H5NH2 >NH3
And (CH3)2NH > CH3NH2 > (CH3)3N >NH3