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My notes from my teacher says that 1- chloromethylpropane can be prepared from methylpropane under sunlight with chlorine.

However I am confused as I think there is no such thing as methylpropane because it is actually butane.

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  • $\begingroup$ en.wikipedia.org/wiki/Isobutane#Nomenclature $\endgroup$
    – andselisk
    Feb 26 at 11:32
  • $\begingroup$ Ironically if you Wikipedia'd methylbutane, which takes you straight to isobutane, you would have saw the difference, making the 2nd part of your question unnecessary. $\endgroup$ Feb 26 at 11:45
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    $\begingroup$ Obviously not: it is dimethyl ethane. ;-) $\endgroup$
    – matt_black
    Feb 26 at 13:12

1 Answer 1

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Above: methylpropane, Below: butane

The bottom molecule is butane and the top is methylpropane.

The suffix -ane implies a molecule containing only carbon-carbon and carbon-hydrogen single bonds, which can be seen in both compounds.

The prefix but- implies that the longest continuous carbon chain in the molecule is four carbon atoms long. Note that every carbon atom in butane constitutes such a chain (which is why there is no need to mention substituents - there are none)

However, if you look at methylpropane and try to find the largest continuous chain, it is impossible to include all four carbon atoms. As evident in the numbering, the longest such chain that can be produced is 3 carbon atoms long, (as the fourth carbon atom is always attached to the second one in chain - this is important) which is indicated with the prefix prop-.

Therefore, we need to add the prefix methyl- to indicate a substituent of one carbon atom bonded to three hydrogen atoms. We usually add a number (such as 2-) before this prefix to indicate which base chain carbon atom the substituent is attached to. In this case, it is not required. To see why, think about how the length of the longest continuous carbon chain would change if the fourth carbon atom was instead attached to the third or first in the original chain, and how this change would affect how we name the molecule.

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