The molecular formula C5H12 contains how many isomeric alkanes?

To determine the number of isomeric alkanes in the molecular formula C5H12, we need to consider the different ways in which the carbon atoms can be arranged and connected. Isomers are compounds with the same molecular formula but different structural arrangements.

Step 1: Determine the number of carbon atoms
The formula C5H12 tells us that there are 5 carbon atoms in the molecule.

Step 2: Determine the number of hydrogen atoms
The formula C5H12 tells us that there are 12 hydrogen atoms in the molecule.

Step 3: Determine the maximum number of hydrogen atoms
To find the maximum number of hydrogen atoms that can be attached to 5 carbon atoms, we use the formula 2n + 2, where n is the number of carbon atoms. In this case, the maximum number of hydrogen atoms is 2(5) + 2 = 12.

Step 4: Determine the number of isomeric alkanes
Now we need to consider the different ways in which the carbon atoms can be arranged and connected to form alkanes.
- Linear chain alkanes: In this arrangement, all the carbon atoms are connected in a straight line. There is only one possible linear chain alkane for C5H12, which is pentane.
- Branched alkanes: In this arrangement, some of the carbon atoms are connected to each other in a branched manner. To determine the number of possible branched alkanes, we need to consider the different ways in which the carbon atoms can be arranged in branches.
- For C5H12, there are 3 possible arrangements of branches:
- One branch with 3 carbon atoms and one branch with 1 carbon atom.
- One branch with 2 carbon atoms and one branch with 2 carbon atoms.
- Two branches with 2 carbon atoms each.
- Therefore, there are 3 possible branched alkanes for C5H12.

Conclusion:
Combining the linear chain alkane (pentane) and the branched alkanes, the molecular formula C5H12 contains a total of 4 isomeric alkanes.
Therefore, the correct answer is option 'C' (3).