Question

Name each of the following compounds?

Answer 1

`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 `"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 `(2)`, then that gives us the name of the sidechain attached to the four-carbon "main chain".

The sidechain is `-"CH"_3`, which is a one-carbon alkyl group called `"methyl"`. We replace `"ane"` with `"yl"` because it is a fragment and not the entire compound "methane".

So, the compound is called `bb(2-"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 (`"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 (`"Cl"^(-)`) has a `1-` charge, and each ammine ligand (`"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 + (-1) = +2`

`=> x = color(blue)(+3)`

`=> [stackrel(+3)"Cr"stackrel(0)(("NH"_3)_5)stackrel(-1)"Cl"]^(2+)`

So, we have `"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"`

`=> "pentammine" + "chloro" + "chromium(III)" + "nitrate"`

`=> color(blue)("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"/"Lambda` or `"fac/mer"` isomers, etc.)