The observed carbon-carbon sigma bond length in 1,3-butadiene is 1.48 Å while that in ethane is 1.53 Å .explain?

Give reason:

C2-C3 in 1,3-butadiene is shorter than in n-butane.

Give reason:

C-Cl bond length in chlorobenzene is shorter than expected.

Why the C-Cl bond length in cyanogens is even shorter than that predicted value?

Give reason:

C-Cl bond length in cyanogen chloride is 1.63Å while in methyl chloride is 1.77Å.

What reason is responsible for bond contraction in cyclooctatetraene?

Give reason:

Cyclooctatetraene exists in a puckered conformer not in planar structure.

Give reason:

The C-NO2 bond length for 4-nitroaniline (1.43Å) is shorter than

that in nitrobenzene (1.49Å).

Give reason:

In 2,4,6-trinitroiodobenzene(picryl iodide), the para C-N bond length is shorter than that the ortho C-N bond.

or

The C-N bond length is 1.35Å for the p-NO2 and 1.45Å for o-NO2 in picryl iodide. (Normal C-N is 1.47Å and C=N is 1.28Å)

Give reason:

1. The resonance energy for 1,3-butadiene is 3.5 kcal/mole

2. The resonance energy of benzene is 36 kcal/mole.

Give reason:

1. Acetaldehyde exists in keto form.

2. Acetylacetone exists in the enol form (80%) while ethyl acetoacetate (75%).

3. phloroglucinol reacts in keto form as well as in the enol form.

Give reason:

Methyl iodide is more reactive than methyl chloride towards nucleophilic substitution reactions.

Give reason:

1. N,N-dimethylaniline can coupled with diazonium cation while 2,6,N,N-tetramethylaniline can’t.

2. The dipole moment of N,N-dimethylaniline is 1.61D while 2,6,N,N-tetramethylaniline is 0.94D.