Problem 5 - Campbell Biology Concepts & Connections

Question

Of the following functional groups, which is/are polar, tending to make organic compounds hydrophilic? a. carbonyl b. amino c. hydroxyl d. all of the above

Step-by-Step Solution

Answer

d. all of the above

Step 1: Analyze the Carbonyl Group

The carbonyl group consists of a carbon atom double-bonded to an oxygen atom (C=O). This group is polar because the oxygen atom is more electronegative than the carbon atom, creating a partial negative charge on the oxygen and a partial positive charge on the carbon. This polarity makes compounds containing the carbonyl group hydrophilic.

Step 2: Analyze the Amino Group

The amino group consists of a nitrogen atom bonded to two hydrogen atoms (—NH2). This group is polar because nitrogen is more electronegative than hydrogen, creating a partial negative charge on the nitrogen and partial positive charges on the hydrogen atoms. This polarity makes compounds containing the amino group hydrophilic.

Step 3: Analyze the Hydroxyl Group

The hydroxyl group consists of an oxygen atom bonded to a hydrogen atom (—OH). This group is polar because oxygen is more electronegative than hydrogen, creating a partial negative charge on the oxygen and a partial positive charge on the hydrogen. This polarity makes compounds containing the hydroxyl group hydrophilic.

Step 4: Conclusion

Since the carbonyl, amino, and hydroxyl groups are all polar and tend to make organic compounds hydrophilic, the correct answer is: all of the above.

Key Concepts

Carbonyl Group

The carbonyl group is an important functional group in organic chemistry. It consists of a carbon atom double-bonded to an oxygen atom, represented as C=O. This double bond creates a polar region in a molecule.
Oxygen is more electronegative than carbon, which means it attracts electrons more strongly. This results in a partial negative charge on the oxygen and a partial positive charge on the carbon.
This difference in charge distribution makes the carbonyl group polar, contributing to the molecule's hydrophilic (water-loving) nature.

Amino Group

The amino group is another crucial functional group, represented as —NH2. It consists of a nitrogen atom bonded to two hydrogen atoms.
Similar to the carbonyl group, the amino group is polar. Nitrogen is more electronegative than hydrogen, causing a partial negative charge on the nitrogen and partial positive charges on the hydrogen atoms.
This polarity helps the amino group interact well with water, making compounds that contain amino groups hydrophilic.
Amino groups are commonly found in amino acids, the building blocks of proteins.

Hydroxyl Group

The hydroxyl group, often represented as —OH, consists of an oxygen atom bonded to a hydrogen atom.
Oxygen's high electronegativity compared to hydrogen creates a partial negative charge on the oxygen and a partial positive charge on the hydrogen.
This makes the hydroxyl group polar and hydrophilic.
Hydroxyl groups are a key feature in alcohols and many other organic molecules, helping them dissolve in water.

Polarity

Polarity is a fundamental concept in chemistry that describes the distribution of electric charge around molecules.
When atoms in a molecule have significantly different electronegativities, one atom pulls electrons more strongly than the other.
This creates partial positive and negative charges, making the molecule polar.
Polar molecules tend to be hydrophilic because they can form hydrogen bonds and other electrostatic interactions with water molecules.
Understanding polarity helps explain why certain functional groups like carbonyl, amino, and hydroxyl groups can make a molecule hydrophilic.