The functional group which does NOT contain oxygen hetero atom is:

The correct answer is halo alkane.

Step-by-Step Explanation:

1. Understanding Heteroatoms:
In organic chemistry, a heteroatom is any atom in an organic molecule that is not carbon (C) or hydrogen (H). Common heteroatoms include oxygen (O), nitrogen (N), sulfur (S), and halogens (F, Cl, Br, I).

2. Analyzing the Functional Groups:

• Ketone: Contains a carbonyl group ($-\text{C}=\text{O}$). The heteroatom present here is oxygen.

• Carboxylic acid: Contains a carboxyl group ($-\text{COOH}$). It contains two oxygen atoms as heteroatoms.

• Alcohol: Contains a hydroxyl group ($-\text{OH}$). The heteroatom present here is oxygen.

• Halo alkane: Formed by replacing one or more hydrogen atoms in an alkane with a halogen atom ($-\text{X}$, where X = F, Cl, Br, or I). The heteroatom present here is a halogen, not oxygen.

3. Conclusion:
Among the given options, only halo alkane does not contain an oxygen heteroatom.