NMR Flashcards

1
Q

What is the standard?

A

Tetramethylsilane TMS, Si(CH3)4

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2
Q

How do the different peaks come about?

A

Chemically equivalent hydrogen atoms are all in the same chemical environment and appear at the same chemical shift. A hydrogen atom in a chemical environment has its nucleus exposed.

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3
Q

What does deshielded mean?

A

The further away the bonded electrons are from the proton the more deshielded the proton. This is caused from being attached to a very electronegative atom.

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4
Q

Why is TMS used?

A

It has 12 hydrogen environments which are all chemically equal which produce a single peak. The hydrogens are less deshielded than any other H atoms in an organic compound, wont interfere with the other peaks and its inert.

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5
Q

What is the label for the horizontal axis?

A

Chemical shift 𝞭, and has units ppm

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6
Q

What does the sets of peaks equal?

A

The number of hydrogen environments

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7
Q

What does the area under each peak equal?

A

The ratio of the number of hydrogens in each chemical environment

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8
Q

What is the n+1 rule?

A

The spin-spin splitting pattern is caused by hydrogen atoms bonded to adjacent carbon atoms

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9
Q

What is the difference between low and high resolution?

A

Low resolution does not show splitting pattern, High resolution does show the splitting pattern

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10
Q

Where do the peaks occur if the hydrogen atoms are bonded to very electronegative atoms?

A

Are deshielded and appear more downfield

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11
Q

Where do peaks occur if the hydrogen atoms are in alkyl groups?

A

Less deshielded and appear more upfield.

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