Tag: introduction to organic chemistry

Questions Related to introduction to organic chemistry

In which compound enol form is maximum

  1. $CH _3-\overset{\overset{O}{||}}C-CH _3$

  2. ${ CH } _{ 3 }-CH=O$

  3. ${ CH } _{ 3 }-\underset { || }{ C } -{ CH } _{ 2 }-CH _3\ \quad \quad \quad  O$

  4. ${ CH } _{ 3 }-{ CH _2 } -{ CH } _{ 3 }\ \quad \quad \quad \quad $


Correct Option: C

2 mole of ${ H } _{ 3 }{ PO } _{ 4 }$ has:

  1. Two $\pi $-bond

  2. Seven mole of $\sigma $-bond

  3. Sixteen lone pair of electron

  4. Fourteen mole of $\sigma $-bond


Correct Option: D

Geometry as sulphur is bent in 
I.${S} _{8}$ II.$S{F} _{2}$  III.$S{O} _{2}$

  1. I, II, III

  2. I, II

  3. II, III

  4. I, III


Correct Option: C
Explanation:

i. $S _8$ has rhombic shape.

ii.$SF _2$ has two lone pair and two particles geometry of $SF _2$ is bent or angular.
iii. $SO _2$ has one lone pair and $2$ oxygen molecules which gives bent geometry.

The enthalpy of reaction,${\text{2HC}} \equiv {\text{CH + 5C}}{{\text{O}} _{\text{2}}}{\text{ + 2}}{{\text{H}} _{\text{2}}}{\text{O}}\,$
 If the bounds energies of ${\text{C - H,C}} \equiv {\text{C,}}\,{\text{O = O,C = O}}$ abd ${\text{O - H}}$ bounds are p,q,r,s,t respectively 

  1. $\left[ {8s + 4t} \right] - \left[ {4p + q + 5r} \right]$

  2. $\left[ {4p + 2q + 5r} \right] - \left[ {8s + 4t} \right]$

  3. $\left[ {4p + 2q + 5r + 8s + 4t} \right]$

  4. $\left[ {2q + q + 5r + } \right] - \left[ {8s + 4t} \right]$


Correct Option: A

Decreasing order of bond length of marked carbon oxygen bounds 

  1. $\alpha > \beta >\gamma $

  2. $\beta >\gamma > \alpha $

  3. $\beta >\alpha >\gamma $

  4. $\gamma > \beta > \alpha $


Correct Option: D

The number of $\displaystyle \sigma-bond$ and $\displaystyle \pi- bond$ in $HCN$ are respectively:

  1. $2$ and $2$

  2. $1$ and $3$

  3. $2$ and $1$

  4. None of these


Correct Option: A
Explanation:

$H-C\equiv N$ contains $2$ sigma bonds and $2$ pi bonds.

Which of the following is not correct?

  1. A sigma bond is weaker than pi bond.

  2. A sigma bond is stronger than pi bond.

  3. A double bond is stronger than a single bond.

  4. A double bond between two atoms is shorter than a single bond between the same atoms.


Correct Option: A
Explanation:

A sigma bond is stronger than a $\pi$ bond due to axial overlapping of the orbitals.

A double bond is stronger than a single bond since now more energy is required to break two bonds.
Double bonds are $sp^2$ hybridized and are shorter in length.
Hence, the correct option is A.

Assertion: $\sigma$  is strong while $\pi$  is a weak bond.


Reason : Atoms rotate freely about  $\pi$  bond.

  1. Both assertion and reason are true, and reason is not the true
    explanation of the assertion.

  2. Both assertion and reason are true, but reason is the true
    explanation of the assertion.

  3. Assertion is true, but reason is false

  4. Both assertion and reason are false.


Correct Option: C
Explanation:

$\sigma$ bond is stronger than $\pi$ bond because in $\sigma$ bond the overlap is axial while in $\pi$ bond. It is lateral.


Due to the lateral overlap in $\pi$ bond atoms cannot rotate freely in $\pi$ bond.
So, assertion is true and reason is false.

The sigma bond energy of $C-H$ bond in $C _{2}H _{6}$ is:

  1. $99\ kcal$

  2. $140\ kcal$

  3. $200\ kcal$

  4. $60\ kcal$


Correct Option: B

In carbon-hydrogen-oxygen compounds:

  1. all $O-$ to $-H$ bonds are $\pi$ bonds

  2. all $C-$ to $-H$ bonds are $\sigma $ bonds

  3. all $C-$ to $-C$ bonds are $\sigma $ and/or $\pi$ bonds

  4. all $C-$ to $-C$ bonds are $\pi$ bonds


Correct Option: B,C