Chapter U2.13, Problem 3E

Interpretation Introduction

Interpretation : Minimum amount of information that is needed in predicting the sweet smell of a compound is to be identified.

Concept Introduction :

Molecules smell differently due to different arrangement of atoms, different functional groups and different shapes. The chemistry behind smell is very complicated. There are many ways by which one can predict smell of a compound. These are molecular formula, functional group, chemical name and overall shape of the molecule.

Answer to Problem 3E

Minimum amount of chemical information needed to predict sweet smell are:

• Functional group- A sweet smelling compound may have a hydroxyl group or a ketone or an ester group.
• Molecular shape- The overall shape of the molecule can help in predicting the sweet smell. If the shape is long and stringy it means the compound has sweet smell. If the molecule is ball shaped it will smell like camphor and if shape is flat, it will have minty smell.

Explanation of Solution

Minimum information needs to predict sweet smell is knowledge of functional group and shape of the molecule.

• Functional group- A sweet smelling compound may have a hydroxyl group or a ketone or an ester group. So first one need to know the functional group present in the compound. This will rule out the molecules with putrid and fishy smells.
• Overall shape of the molecule- The molecular shape is an accurate predictor of many smells. Camphor smelling compounds have ball shaped molecules while minty compounds have flat molecules. Long and stringy molecules often smell sweet. So by knowing the shape of the molecule one can rule out camphor and minty smells due to presence of hydroxyl and ketone groups. If the shape is stringy it means the molecule will have sweet smell.

Minimum amount of chemical information that is needed in predicting sweet smell is the functional group and the shape of the molecule.

Conclusion

Although all chemical information is valuable at different times in predicting different kind of smell, the shape of the molecule and functional groups are most important.