[Defiledxhalo]

Hello!  Below is the homework problem:

Which of the following isomeric dibromopropanes has only a single peak in its proton NMR spectrum?
A. 1,1-dibromopropane
B. 1,3-dibromopropane
C. 1,2-dibromopropane
D. 2,2-dibromopropane

I have a feeling it's not either B nor C, so that just leaves A or B.  I'm having a hard time grasping the NMR concept in our class and my textbook doesn't really give a great explanation about it, so if anyone would like to explain to me why the answer is either A or B (or if I narrowed it down completely wrong), or link me to a detailed tutorial on how to solve problems like this, I'd appreciate it a lot!

[Guitarmaniac86]

Draw structure D. How many protons are on the central carbon? How many protons are on the terminal carbons. If the molecule is symmetric, will the protons be equivalent? If they are equivalent, how many peaks in the proton NMR will you see?

[surviving]

As guitarmaniac86 stated, drawing these out will be immensely helpful. Peaks on proton NMR spectra are determined by H atoms in unique chemical environments. Peak splitting (which you're looking at) is determined by how many protons the neighboring carbon(s) has(have).

to find the number of peaks, what you do is take the number of hydrogens on adjacent carbons and add 1. Two hydrogens on adjacent carbons would be three peaks, four would be five peaks. This should *delete me*

[discodermolide]

Your statement is somewhat misleading. Just counting hydrogens and adding one does not give you the peak shape, i.e. is it a doublet, or a triplet. The intensities of the lines in the peak is also very important. They follow the Pascal's triangle system.
The splitting of the peaks tells you immediately what that particular atom is coupled to.

[surviving]

you're correct, i shouldn't have assumed that he hasn't studied j-coupling yet.