Question

Write down the IUPAC name of the following organic compound: $CH_2=CHCHOH-CH_2CHO$

Answer 1

To find out the IUPAC name first draw the structure of the given molecule to get more clarity of the types of bonds and functional groups present. Doing that will help in identifying the longest carbon chain (parent chain) and also about different substituents. Remember the IUPAC nomenclature rules and proceed in a systematic manner.

Complete answer:
The structure of the given compound is as shown below:

Now identify the longest carbon chain and start numbering the order of preference.
Since we have an aldehyde group ($- CHO$) present here, that has to be given priority. So the numbering will be as follows:

Since the chain is 5 Carbon long the parent chain can be named as pentane
Now since we have a double bond present at the 4th carbon we will have to rename the parent as pent-4-ene
There is a hydroxyl group in the 3rd carbon position and therefore the name becomes 3-Hydroxy-pent-4ene
The main functional group in this compound is the aldehyde group and therefore we have to indicate that by adding –al as a suffix
Thus the IUPAC name of the compound becomes 3-Hydroxy-pent-4-en-1-al

Note:
When adding suffixes like “-al”,”-ol”,”-one” after the words “ane”,“ene”,”yne”, the“e” is dropped. i.e., an “e” is dropped if the letter following it is a vowel: “prop-3-en-1-ol”, not “3- pent-3-ene-1-ol”.
Take care that when the substituents are written in the IUPAC name, they should be in the alphabetical order. E.g. 3-chloro-2-methylpropane not 2-methyl-3-chloropropane