(i)
(ii)
(iii)
The correct order of C = O bond length in ethyl propanoate(I), ethyl propenoate(II) and ethenyl propanoate(III) is
(ii)(iii)The correct order of C = O bond length in ethyl propanoate(I), ethyl propenoate(II) and ethenyl propanoate(III) is
- I>II>III
- III>II>I
- I>III>II
- II>I>III
The Correct Option is D
Solution and Explanation
Let’s understand the structure and resonance in each compound:
- Ethyl propanoate (I): CH3CH2COOCH2CH3
→ No conjugation with the carbonyl (C=O) group. So, it has a typical ester C=O bond length. - Ethyl propenoate (II): CH2=CH–COOCH2CH3
→ The carbonyl group is conjugated with the adjacent C=C double bond (alkene), which causes resonance.
→ This partial delocalization lengthens the C=O bond slightly, making it longer than in (I). - Ethenyl propanoate (III): CH3CH2COOCH=CH2
→ The vinyl group is attached to the –OR part (not conjugated with the C=O group).
→ But –OCH=CH2 can still donate some electron density through resonance, increasing delocalization over the ester group.
Now consider the resonance effects:
- Conjugation with the C=O group increases delocalization and results in longer C=O bonds.
- More conjugation → more delocalization → longer C=O bond.
So, the bond length order is:
II (most conjugation, longest C=O) > I (normal ester) > III (least conjugation affecting C=O)
Correct order: II > I > III
Correct answer: Option (D)
Top Questions on Chemical bonding and molecular structure
Identify the correct orders against the property mentioned:
A. H$_2$O $>$ NH$_3$ $>$ CHCl$_3$ - dipole moment
B. XeF$_4$ $>$ XeO$_3$ $>$ XeF$_2$ - number of lone pairs on central atom
C. O–H $>$ C–H $>$ N–O - bond length
D. N$_2$>O$_2$>H$_2$ - bond enthalpy
Choose the correct answer from the options given below:- NEET (UG) - 2025
- Chemistry
- Chemical bonding and molecular structure
- Identify the geometry and hybridization of the central atom in SF₄.
- BITSAT - 2025
- Chemistry
- Chemical bonding and molecular structure
- A group 15 element forms \( d\pi - d\pi \) bond with transition metals. It also forms a hydride, which is the strongest base among the hydrides of other group members that form \( d\pi - d\pi \) bonds. The atomic number of the element is ________________________.
- JEE Main - 2025
- Chemistry
- Chemical bonding and molecular structure
- What is the bond order for diatomic carbon according to molecular orbital theory?
- AIIMS Paramedical - 2025
- Chemistry
- Chemical bonding and molecular structure
- Which of the following has $\text{sp}^3\text{d}^2$ hybridisation?
- JEE Main - 2025
- Chemistry
- Chemical bonding and molecular structure
Questions Asked in WBJEE exam
- Ruma reached the metro station and found that the escalator was not working. She walked up the stationary escalator with velocity \( v_1 \) in time \( t_1 \). On another day, if she remains stationary on the escalator moving with velocity \( v_2 \), the escalator takes her up in time \( t_2 \). The time taken by her to walk up with velocity \( v_1 \) on the moving escalator will be:
- WBJEE - 2025
- Relative Motion
A quantity \( X \) is given by: \[ X = \frac{\epsilon_0 L \Delta V}{\Delta t} \] where:
- \( \epsilon_0 \) is the permittivity of free space,
- \( L \) is the length,
- \( \Delta V \) is the potential difference,
- \( \Delta t \) is the time interval.
The dimension of \( X \) is the same as that of:- WBJEE - 2025
- Dimensional Analysis
- Which logic gate is represented by the following combination of logic gates?
- WBJEE - 2025
- Logic gates
- The variation of displacement with time of a simple harmonic motion (SHM) for a particle of mass \( m \) is represented by: \[ y = 2 \sin \left( \frac{\pi}{2} + \phi \right) \, \text{cm} \] The maximum acceleration of the particle is:
- WBJEE - 2025
- simple harmonic motion
- A force \( \mathbf{F} = ai + bj + ck \) is acting on a body of mass \( m \). The body was initially at rest at the origin. The co-ordinates of the body after time \( t \) will be:
- WBJEE - 2025
- Newtons Laws of Motion
Concepts Used:
Chemical Bonding and Molecular Structure
Such a group of atoms is called a molecule. Obviously, there must be some force that holds these constituent atoms together in the molecules. The attractive force which holds various constituents (atoms, ions, etc.) together in different chemical species is called a chemical bond.
Types of Chemical Bonds:
There are 4 types of chemical bonds which are formed by atoms or molecules to yield compounds.
- Ionic Bonds - Ionic bonding is a type of chemical bonding which involves a transfer of electrons from one atom or molecule to another.
- Covalent Bonds - Compounds that contain carbon commonly exhibit this type of chemical bonding.
- Hydrogen Bonds - It is a type of polar covalent bonding between oxygen and hydrogen wherein the hydrogen develops a partial positive charge
- Polar Bonds - In Polar Covalent chemical bonding, electrons are shared unequally since the more electronegative atom pulls the electron pair closer to itself and away from the less electronegative atom.
Factors Affecting Bond Enthalpy in Chemical Bonding:
- Size of the Atom
- Multiplicity of Bonds
- Number of Lone Pair of Electrons Present
- Bond Angle