Tag: introduction to organic chemistry

Quizzes (1) Questions (38)

Questions Related to introduction to organic chemistry

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

$Mg _2C _3$ reacts with water to form propyne. $C _3^{4-}$ has:

  1. two sigma and two pi bonds

  2. three sigma and one pi bonds

  3. two sigma and one pi bonds

  4. two sigma and three pi bonds
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

${ Mg } _{ 2 }{ C } _{ 3 }+{ 4H } _{ 2 }O\longrightarrow { Mg(OH) } _{ 2 }+{ C } _{ 3 }{ H } _{ 4 }$ Propyne
$ { C } _{ 3 }^{ 4- }  ion $

$\left[ C\equiv C-C \right] ^{ 4- }$
$2 \, \Pi $ Bonds
$2\,\sigma$ Bonds

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Give the number of $\sigma$ and $\pi$ bonds in (i)$C^{2-} _2$ (ii)$C _3^{4-}$ and (iii)$CN^{2-} _2.$

  1. (i) 2 $\sigma$, 1 $\pi$; (ii) 1 $\sigma$, 3 $\pi$; (iii) 2 $\sigma$, 2 $\pi$
  2. (i) 2 $\sigma$, 1 $\pi$; (ii) 3 $\sigma$, 1 $\pi$; (iii) 2 $\sigma$, 2 $\pi$
  3. (i) 1 $\sigma$, 2 $\pi$; (ii) 2 $\sigma$, 2 $\pi$; (iii) 2 $\sigma$, 2 $\pi$
  4. (i) 1 $\sigma$, 2 $\pi$; (ii) 3 $\sigma$, 1 $\pi$; (iii) 2 $\sigma$, 2 $\pi$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$(i)^{-}\textrm{C}\equiv C^-$  one $\sigma$, two $\pi$;  (ii) $^{-}\textrm{C}\equiv C-C^{3-}$ two $\sigma$, two $\pi$;   (iii) $^{-}\textrm{N}=C=N^-$ two $\sigma$, two $\pi$
Hence option C is correct.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Which of the following compound has a lowest nitrogen-nitrogen bond length?


     $N _2,  N _2H _2,  N _2F _2$.

  1. $N _2$
  2. $N _2H _2$
  3. $ N _2F _2$

  4. All have equal bond length.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

N2 has a triple bond (bond order 3), N2H2 has a double bond (bond order 2), and N2F2 has a double bond. Higher bond order results in shorter bond length.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Select  the incorrect statement.

  1. Double bond is shorter than a single bond
  2. $\sigma$-bond is weaker than a $\pi$-bond

  3. Double bond is stronger than a single bond

  4. Covalent bond is stronger than hydrogen bond
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A sigma bond is generally stronger than a pi bond because of greater orbital overlap. Therefore, the statement that a sigma bond is weaker than a pi bond is incorrect.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Which of the following has $p _{\pi}-d _{\pi}$ bonding?

  1. $NO _3^-$
  2. $SO _3^{2-}$
  3. $BO _3^{3-}$
  4. $CO _3^{2-}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$p \pi-p \pi$ bonding: If there is bonding between two atoms where one atom is having one vacant orbital and another is having one lone pair of electrons, then this electron pair is donated to that respective vacant orbital. This type of bonding is called $p \pi-p \pi$   or $p \pi-d \pi$ depending on the orbital to which the electron pair is donated and from which the electron pair is donated.

In the above options $SO _3^{-2}$ forms $p \pi-p \pi$ bonding.
Hence option $B$ is correct.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

Which of the following statement is not correct for sigma and pi-bonds formed between two carbon atoms?

  1. A sigma bond is stronger than a pi-bond.

  2. Bond energies of sigma and pi-bonds are of the same order.

  3. Free rotation of atoms about a sigma bond is allowed but not in case of a pi-bond.

  4. A sigma bond determines the direction between carbon atoms, but a pi-bond has no primary effect in this regard.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A) A sigma bond is stronger than a pi-bond. This is because sigma bond is formed by axial overlap and pi bond is formed by lateral overlap. Thus the extent of overlap is greater in sigma bond formation than in pi bond formation.
Hence, the option A is correct.
B) Bond energy of sigma bond is higher than that of pi bond as sigma bond is stronger than pi bond.
Hence, the option B is incorrect.
C) Free rotation of atoms about a sigma bond is allowed but not in case of a pi-bond. When the carbon atoms of sigma bond are rotated, the axial overlap is not affected. but in case of pi bonds, the lateral overlap will be affected.
Hence, the option C is correct.
D) A sigma bond determines the direction between carbon atoms, but a pi-bond has no primary effect in this regard. A pi bond is present only when a sigma bond is already present.
hence, the option D is correct.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

In allene structure, three carbon atoms are joined by :

  1. three $\sigma$- and three $\pi$-bond
  2. two $\sigma$- and one $\pi$-bond
  3. two $\sigma$- and two $\pi$ - bonds
  4. three $\pi$- bonds only
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

 Allene is $CH _{2}\, =\, C\, =\, CH _{2}$.
The terminal carbons each form one $ \sigma$ with the central carbon. The other bond formed by the terminal carbon with the central carbon is a $\pi$ bond. Hence in total there are two $\sigma$- and two $\pi$ - bonds.

Multiple choice chemistry introduction to organic chemistry bonding in organic molecule tetravalence of carbon: shapes of organic compounds introduction to carbon and its compounds

A triple bond is made of :

  1. one $\sigma$- and two $\pi$ - bonds
  2. two $\sigma$- and one $\pi$ - bonds
  3. three $\sigma$- and three $\pi$ - bonds
  4. one $\sigma$- and four $\pi$ - bonds
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A triple bond is made of one $\sigma $-bond and two $\pi$-bonds.

So answer is A.