# Name each of the following compounds?

Dec 5, 2016

A)

The first one is a kind of hydrocarbon. When we identify the main chain, we can create the parent name to the IUPAC name.

The main chain has $4$ carbons (here, it is depicted horizontally), which corresponds to the prefix $\text{but} -$. This has no double bonds or triple bonds, so it is a plain ol' alkane.

Therefore, this compound is some sort of butane-based compound, resembling this:

If we number the main chain carbons (in accordance with IUPAC Nomenclature rules) so that each sidechain is the lowest number possible $\left(2\right)$, then that gives us the name of the sidechain attached to the four-carbon "main chain".

The sidechain is $- {\text{CH}}_{3}$, which is a one-carbon alkyl group called $\text{methyl}$. We replace $\text{ane}$ with $\text{yl}$ because it is a fragment and not the entire compound "methane".

So, the compound is called $\boldsymbol{2 - \text{methylbutane}}$.

B)

In this inorganic transition metal complex, we take a somewhat different approach and look at the charge of the outer ligand (on the second coordination sphere).

["Cr"("NH"_3)_5"Cl"]stackrel("Nitrate")overbrace(("NO"_3)_2)

Each nitrate ion (${\text{NO}}_{3}^{-}$) actually has a $1 -$ charge, and there are two of them. So, the part of the formula in square brackets is going to balance out and have a $2 +$ charge.

stackrel("+2 charge")overbrace(["Cr"("NH"_3)_5"Cl"])stackrel("-1 charge each")overbrace(("NO"_3)_2)

This polyatomic ion's name is simply going to be appended, like when naming any ionic compound with two ions (such as silver nitrate, or calcium nitrate).

The chloro ligand (${\text{Cl}}^{-}$) has a $1 -$ charge, and each ammine ligand (${\text{NH}}_{3}$) is actually neutral.

These ligands in the inner coordination sphere will have prefixes indicating how many of each there are, except if there is $1$.

Also, if the prefix ends in a vowel and the ligand starts with a vowel, the double vowel is omitted. So, "pent" will go in front of "ammine".

The remaining charge has to balance out to give $2 +$:

$x + \left(- 1\right) = + 2$

$\implies x = \textcolor{b l u e}{+ 3}$

$\implies {\left[\stackrel{+ 3}{\text{Cr"stackrel(0)(("NH"_3)_5)stackrel(-1)"Cl}}\right]}^{2 +}$

So, we have ${\text{Cr}}^{3 +}$ in our transition metal complex.

Put that all together in all lowercase without a space (except for the appended anion name), in alphabetical order of ligand name:

stackrel("alphabetical order of ligand name")overbrace("prefix" + "ligand" + . . . + "prefix" + "ligand") + "metal"("oxid. number") + "anion name"

$\implies \text{pentammine" + "chloro" + "chromium(III)" + "nitrate}$

$\implies \textcolor{b l u e}{\text{pentamminechlorochromium(III) nitrate}}$

And since only one ligand differs in the inner coordination sphere, there is no special symmetry that we should account for in the naming.

(No cis/trans, no $\Delta \text{/} \Lambda$ or $\text{fac/mer}$ isomers, etc.)