NMR Spectroscopy

alanan84 · Jul 20, 2008

What is the best way to tell if atoms are equivalent? Do you look directly at what the carbon is bonded to or what? I'm a little confused with this.

PooyaH · Jul 20, 2008

alanan84 said:
What is the best way to tell if atoms are equivalent? Do you look directly at what the carbon is bonded to or what? I'm a little confused with this.

You mean with acids and bases?

alanan84 · Jul 21, 2008

PooyaH said:
You mean with acids and bases?

No, this may be really basic but I want to make sure I understand. Here's an example question.

How many signals does 1,3,5 tribromobenzene have in its 13C NMR spectrum?

So you would need to identify the equivalent and nonequivalent carbons right?

AdaAda87 · Jul 21, 2008

There are two Carbon signals, okay so first draw out the compound and then you'll see the bromines, so at the middle there is one, and at the bromine is the second one. Get it? all the others are the same, just rotated.

Thundercatz · Jul 21, 2008

alanan84 said:
No, this may be really basic but I want to make sure I understand. Here's an example question.

How many signals does 1,3,5 tribromobenzene have in its 13C NMR spectrum?

So you would need to identify the equivalent and nonequivalent carbons right?

Best way to test if atoms are equivalent is stick something like Br on the two atoms in question. If the name of molecule changes, the two atoms are not equivalent. For example, lets say you have butane and wanted to see if the hydrogens on carbon 2 and 3 are equivalent or not. Replace one hydrogen on carbon number 2 and you will have 2-bromobutane. Now replace one hydrogen on carbon 3 and you still have 2-bromobutane. Since the name of the molecules is the same, the hydrogens are equivlanet.

PooyaH · Jul 21, 2008

Thundercatz said:
Best way to test if atoms are equivalent is stick something like Br on the two atoms in question. If the name of molecule changes, the two atoms are not equivalent. For example, lets say you have butane and wanted to see if the hydrogens on carbon 2 and 3 are equivalent or not. Replace one hydrogen on carbon number 2 and you will have 2-bromobutane. Now replace one hydrogen on carbon 3 and you still have 2-bromobutane. Since the name of the molecules is the same, the hydrogens are equivlanet.

👍👍👍

alanan84 · Jul 21, 2008

Thundercatz said:
Best way to test if atoms are equivalent is stick something like Br on the two atoms in question. If the name of molecule changes, the two atoms are not equivalent. For example, lets say you have butane and wanted to see if the hydrogens on carbon 2 and 3 are equivalent or not. Replace one hydrogen on carbon number 2 and you will have 2-bromobutane. Now replace one hydrogen on carbon 3 and you still have 2-bromobutane. Since the name of the molecules is the same, the hydrogens are equivlanet.

Beautiful, thanks so much. I had read that but for some reason it just made more sense this time!

NMR Spectroscopy

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