The IUPAC name of
`CH_3 CH OH CH_2 CH (CH_3) CHO` is

Options

A. 2-hydroxy-4 methylpentanal
B. 4-hydroxy-2 methylpentanal
C. 2-hydroxy-3 methylpentanal
D. 2-methylpent-4-ol-1-al

Answer

To determine the IUPAC name of the compound `CH3 CH OH CH2 CH(CH3) CHO`, we will follow these steps:

### Step 1: Identify the Structure
The compound can be broken down as follows:
- The first part is `CH3` (methyl group).
- The second part is `CH` with an `OH` group, indicating a hydroxyl group (alcohol).
- The third part is `CH2`.
- The fourth part is `CH(CH3)`, indicating a carbon with a methyl group attached.
- The last part is `CHO`, indicating an aldehyde group.

### Step 2: Determine the Longest Carbon Chain
Count the number of carbon atoms in the longest continuous chain:
- The longest chain here consists of 5 carbon atoms.

### Step 3: Number the Carbon Chain
Number the carbon chain from the end nearest to the functional group with the highest priority. In this case, the aldehyde group (CHO) has the highest priority and should be given the lowest number:
- Start numbering from the aldehyde end:
1. CHO (1)
2. CH2 (2)
3. CH (3)
4. CH(CH3) (4)
5. CH3 (5)

### Step 4: Identify and Name the Substituents
Now identify the functional groups and substituents:
- At carbon 1, we have an aldehyde (CHO).
- At carbon 2, we have a hydroxyl group (OH).
- At carbon 4, we have a methyl group (CH3).

### Step 5: Combine the Names
The IUPAC name is constructed by combining the names of the substituents in alphabetical order followed by the name of the longest chain:
- The substituents are:
- Hydroxy (from the OH group at position 2)
- Methyl (from the CH3 group at position 4)
- The longest chain is pentanal (since it has 5 carbons and ends with an aldehyde).

### Final IUPAC Name
Putting it all together, the IUPAC name is:
**4-hydroxy-2-methylpentanal**