Final answer:
The proton at C4 of 2,3-dimethyl-2-phenylbutane would show a septet splitting pattern due to its adjacent hydrogens and chemical equivalent methyl groups.
Step-by-step explanation:
The proton at C4 of 2,3-dimethyl-2-phenylbutane would show a septet splitting pattern.
To determine the splitting pattern, we need to count the number of adjacent hydrogens. The proton at C4 has 3 adjacent hydrogens: two hydrogens on the carbon next to it (C3) and one hydrogen on the carbon two carbons away (C2). According to the n + 1 rule, the number of peaks in the splitting pattern is given by (n + 1), where n is the number of adjacent hydrogens.
In this case, there are 3 adjacent hydrogens, so the splitting pattern would consist of 3 + 1 = 4 peaks, which corresponds to a quartet. However, since the proton at C4 is also coupled to two chemically equivalent methyl groups (CH3), it would experience additional splitting. Each methyl group would split the signal into a doublet, resulting in a total of 4 x 2 = 8 peaks, which corresponds to a septet splitting pattern.