How can I calculate equivalent hydrogens?

How can I calculate equivalent hydrogens?

One way is to replace each H with a different group and see if you get a different compound.

Example 1. Identify the equivalent hydrogens in 2-methylpropane.

If I replace any of the nine CH₃ atoms with a Cl, I'll always get the same compound: 1-chloro-2-methylpropane. So the nine CH₃ atoms form one set of nine equivalent hydrogen atoms.

If I replace the H atom on C-2, I'll always get a different compound: 2-chloro-2-methylpropane. So this lone H atom forms a second set consisting of 1 hydrogen atom by itself.

Example 2. Identify the equivalent hydrogens in methyl acetate.

If I replace any of the red CH₃ atoms, I'll always get the same compound: methyl chloroacetate. So the red #"H"_"a"# atoms form one set of three equivalent hydrogen atoms.

If I replace any of the blue CH₃ atoms, I'll always get a different compound: chloromethyl acetate. So the blue #"H"_"b"# atoms form a second set of three equivalent hydrogen atoms.

Now that you have the idea, try to identify the equivalent H atoms in ethyl acetate, CH₃COOCH₂CH₃, and the isomeric chloropropanes, C₃H₅Cl.