A compound, HOCH2CH2CH2CH2COCl, reacts with itself to give a new compound. Give the IUPAC name for the starting compound, draw the mechanism for the formation of the new compound and give the prominant feature of the IR spectrum of the new compound.

This compound is highly unstable, and it's IUPAC name would be 5-hydroxypentyl chloride. The "hydroxy" part is from the OH alcohol group, "pent" from the number of carbons in the chain, the "-yl chloride" is from the COCl group, which is the heaviest group, and so is the suffix. The "5" for hydroxy shows that the alcohol group is on the 5th carbon of the chain. 

The OH group is a nucleophile, so will react with the electrophilic COCl group. This is a group is a very strong electrophile, as the Cl draws the electron density away from the C=O bond, making the carbon very electron deficient. The lone pair of electrons on OH attacks the C=O bond, pushing the electrons onto the O. The O- lone pair then comes back down and kicks out the Cl, which is a very good leaving group.As there is nucleophilic attack followed by the loss of a leaving group, this mechanism is a nucleophilic addition-elimination reaction.

The new molecule is a cyclic ester, in a 6 membered ring. In an IR spectrum, the C=O group is strongly absorbing at around 1700 cm-1, so the most prominent peak would be a very sharp peak in that region due to the ester C=O. (Note: you can see that all the starting material has reacted because there would be no large absorbtion peak at around 3000cm-1 from the OH group, as this has all reacted.