[CopperSmurf]

Nice if I could settle a lil' dispute with someone with help from you guys.
If I took an example like ethane in H NMR, I'd expect 2 quartets:

 ||     ||
||||  ||||
----------> B field

but if I took something like CH3CCl3, then we got a problem: there's no hydrogen to compare to on the other carbon! So, would there be no signal?  or would there be a quartet then a singlet? Are all the H NMR signals relative to only the neighboring carbons or are they due to any present H in the molecule?

We're just looking at proton NMR right now and ignoring what'd we would see in C NMR.

[Alpha-Omega]

Here is the link to an excellent NMR tutorial:

http://www.wfu.edu/~ylwong/chem/nmr/h1/

The first topic on the left is "The number of different hydrogens."  You will also want to look at "splitting" 5th choice in the list.

Splitting

NMR provides information on how many hydrogen neighbors exist for a particular hydrogen or group of equivalent hydrogens. In general, an NMR resonance will be split into N + 1 peaks where N = number of hydrogens on the adjacent atom or atoms.

If there are no hydrogens on the adjacent atoms, then the resonance will remain a single peak, a singlet.
If there is one hydrogen on the adjacent atoms, the resonance will be split into two peaks of equal size, a doublet.
Two hydrogens on the adjacent atoms will split the resonance into three peaks with an area in the ratio of 1:2:1, a triplet.
If there are 3 hydrogens on the adjacent atoms, the resonance will be split into four peaks with an area in the ratio of 1:3:3:1, a quartet.  (ref: link above)


This may help you in the future:  www.spectroscopynow.com is a huge knowledgebase for all areas of spectroscopy.  It has resources for the simplest topics and the most difficult.  There are some very nice interactive tutorials available there.

[english]

All three protons are equivalent, but they do not split each other due to quantum mechanical reasons.

Each of the methyl protons has two spin states available for something called population inversion.  This is a quantum mechanical process by which a magnetic nuclide is promoted from a lower energy spin state (with the magnetic field) to a higher energy spin state (against the magnetic field).

However, the splitting patterns of any given proton is not due to the neighboring protons themselves, but rather the available spin states that the neighboring protons can have.  Imagine a proton that is neighboring two identical methylene protons...

X-CH-CH2-Y

These two methylene protons can have different spin assignments (we'll denote a + for spin up proton and a - for spin down proton).  Notice that "+-" is two possibilities, because either neighboring proton can have a spin up or spin down.  These two assignments are identical in energy, hence their side-by-side placement.

++ (highest energy)
+- -+
-- (lowest energy)

This is known as a 1:2:1 triplet.  Look at the ratios.  One "++," two "+-," and one "--."  Notice how many neighboring protons we had.  Two protons therefore gives a triplet (called a 1:2:1 triplet because the triplet signal has one peak twice a intense as the others.)

In your case, the three identical methyl protons do not have any neighboring spin states available, so the signal would just be a singlet. 

It gets very complicated in theory so we'll just leave it at that.

[CopperSmurf]

my friend and I are wrong  . Thanks for clearing everything up!