Question

What are the IUPAC names of the following alkanes?

`A)` `"H"_3"C"-"CH"_2-("CHCH"_3)-"CH"(("CH"_3)_2"CH")-"CH"_3`
`B)` `"H"_3"C"-("CHCH"_2"CH"_3)-"CH"(("CH"_3)_2"CH")-"CH"_3`
`C)` `"H"_3"C"-("CH"_3)_2"C"-("CHCH"_3)-"CH"_2-("CHCH"_3)-"CH"_2-"CH"_3`

Answer 1

Because ALL the molecules are heptane derivatives..........

Explanation:

The longest chain in each of the molecules is seven carbons long, i.e. whatever the name (and by no means am I an expert on nomenclature), we have an heptane derivative.

Now `c.` has correctly identified the longest chain:

`H_3stackrel(1)C-stackrel(2)C(CH_3)_2stackrel(3)CH(CH_3)stackrel(4)CH_2stackrel(5)CH(CH_3)stackrel(6)CH_2stackrel(7)CH_3`

And thus we have, `"2,2,3,5-tetramethylheptane"`.

Claro?

Answer 2

2,3,4-trimethylhexane
2,3,5-trimethylhexane
2,2,3,5-tetraheptane

Explanation:

To answer this kind of question, you should draw the molecular structure. To do this we start with the end of the names. So for A, we start with pentane, which indicates a chain of 5 carbon atoms.
Then we add all the other stuff to this chain. We got a methyl group at carbon atom 3 and an isopropyl group at position 4 at the carbon chain. The same method applies to the other structures

The drawings are shown below.

We can now name this structures using the IUPAC rules. These rules are showed below this answer.

Now have a look at the structures above. I have provided the correct names of the structures in the figure. Also, the correct carbon chain is shown in the blue circle.

Simplified IUPAC Rules

1. Identify and name the longest carbon chain. If there are two chains with an equal amount of carbon atoms, than the one with the most substitutions is the base chain.
2. Name all the groups attached to this chain as alkyl substituents.
3. Number the carbons of the longest chain beginning with the end that is closest to a substituent. (Use alphabetical order if there are 2 substituents at equal distance of the chain). Number the chain in the direction that gives the lower number at the first difference. (so for example instead of 1,3,5 we use 1,7,5)
4. Write the name of the alkane by first arranging all the good substituents in alphabetical order (preceded by carbon number with -): di, tri, tetra, penta, etc