The Question is from neet-chemistry chemical-bonding dipole-moment, and it was created by the author Mr. S M HUSSAIN

Question

Two isomers of $C_3H_6O_2$ have dipole moments of 2.5 D and 0.7 D respectively.  The higher dipole moment is likely associated with which isomer?

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
 **Primary Concept**: Dipole moment and molecular structure
 **Related Topics**: Isomerism, molecular polarity, bond dipoles
 **Prerequisites**: Understanding of electronegativity, bond polarity, and vector addition of dipoles.
## SOLUTION PATHWAY
**Given Information**:
  Two isomers of $C_3H_6O_2$ with dipole moments 2.5 D and 0.7 D.
  Options: Methyl acetate ($CH_3COOCH_3$), Propionic acid ($CH_3CH_2COOH$), Hydroxyacetone ($CH_3COCH_2OH$), 1,3-Propanediol ($HOCH_2CH_2CH_2OH$)
**Method & Steps**:
 1. Analyze the molecular structures of the isomers.
  Reasoning: The dipole moment is a measure of the overall polarity of a molecule.  It depends on the magnitude and direction of individual bond dipoles. Molecules with symmetrical structures often have lower or zero dipole moments because bond dipoles cancel each other out.
 2. Determine which isomer has a more asymmetrical structure.
  Working:  
        * Methyl acetate ($CH_3COOCH_3$) has a relatively large dipole moment due to the significant difference in electronegativity between the oxygen and carbon atoms in the ester group, leading to a substantial dipole moment along the C=O bond and C-O bonds.
        * Propionic acid ($CH_3CH_2COOH$) also possesses a significant dipole moment due to the polar carboxyl group (-COOH). However, the overall symmetry is greater than in methyl acetate.
        * Hydroxyacetone ($CH_3COCH_2OH$) has a dipole moment due to the polar carbonyl group (C=O) and the hydroxyl group (-OH), but the vector sum of these dipoles might be smaller than in methyl acetate.
        * 1,3-Propanediol ($HOCH_2CH_2CH_2OH$) has two hydroxyl groups, but their dipoles are oriented in such a way that the vector sum is likely smaller than in methyl acetate and propionic acid.
  Key Point:  The greater the asymmetry and the larger the difference in electronegativity between atoms, the larger the dipole moment.
 3. Identify the isomer with the higher dipole moment.
  Result: Methyl acetate ($CH_3COOCH_3$) is expected to have the higher dipole moment due to its structure.
  Verification: The given dipole moments support this conclusion; 2.5 D is significantly higher than 0.7 D.
 ## OPTION ANALYSIS
A ✓: Methyl acetate ($CH_3COOCH_3$) has a larger dipole moment (2.5 D) due to the significant polarity of the ester group and the asymmetry of the molecule.
B :x: Propionic acid ($CH_3CH_2COOH$) has a dipole moment, but it's likely smaller than methyl acetate's due to some degree of symmetry.
C :x: Hydroxyacetone ($CH_3COCH_2OH$) might have a dipole moment, but it's likely smaller than methyl acetate's due to the vector addition of dipoles.
D :x: 1,3-Propanediol ($HOCH_2CH_2CH_2OH$) has a relatively small dipole moment due to the partial cancellation of the hydroxyl group dipoles.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Ignoring the vector nature of dipole moments:  Dipoles are vectors, so their direction matters when summing them up.
  2.Oversimplifying molecular symmetry: Even slightly asymmetrical molecules can have significant dipole moments.
 **Quick Tips**:
  1.Look for highly electronegative atoms (like O) and significant differences in electronegativity between bonded atoms.
  2.Consider the overall symmetry of the molecule; symmetrical molecules often have lower dipole moments.

Mr. S M HUSSAIN · Answer

The correct Option is "Methyl acetate ($CH_3COOCH_3$)"

Mr. S M HUSSAIN · Answer

Propionic acid ($CH_3CH_2COOH$)

Mr. S M HUSSAIN · Answer

Hydroxyacetone ($CH_3COCH_2OH$)

Mr. S M HUSSAIN · Answer

1,3-Propanediol ($HOCH_2CH_2CH_2OH$)

NEET Chemistry Chemical Bonding and Molecular Structure Dipole Moment MCQs

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