IUPAC name of HO−CH2−(CH2)3− CH2−COCH3

The IUPAC name of HO−CH2−(CH2)3− CH2−COCH3 is 6-Hydroxyhexan-2-one.

Here's how we get to that:

1. Identify the longest carbon chain in the molecule. In this case, it's a chain of 6 carbon atoms.

2. Identify the functional groups present in the molecule. Here, we have a ketone group (-CO-) and a hydroxyl group (-OH).

3. The ketone group has a higher priority than the hydroxyl group in the IUPAC nomenclature system. Therefore, the ketone group determines the suffix of the name (in this case, -one for ketone) and the position of the carbon atoms (numbering starts from the end of the chain closest to the ketone group).

4. The hydroxyl group is considered as a substituent and is indicated by the prefix 'hydroxy-'.

5. Putting it all together, we have a 6-carbon chain with a ketone group on the 2nd carbon and a hydroxyl group on the 6th carbon. Therefore, the IUPAC name is 6-Hydroxyhexan-2-one.