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Structure Determination Flashcards

(15 cards)

1
Q

When do nuclei have spin?

A

When they have an odd mass number.

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2
Q

How can you change a nuclei’s spin?

A

Change magnetic field strength or let them absorb energy through radio waves.

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3
Q

What is chemical shift measured in?

A

ppm, parts per million

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4
Q

What is the reference compound in NMR?

A

TMS

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5
Q

Why is TMS used as a reference in NMR?

A

It has C and H in the same environments and they are electron rich of will produce a peak far upfield.

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6
Q

What causes samples to be shifted downfield in NMR?

A

Shielding from electrons be it by bonding or electronegative pull.

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7
Q

What does spin-spin coupling show in HNMR?

A

Neighbouring non-equivalent hydrogens on carbons.

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8
Q

How can you work out the number of neighbouring non-equivalent hydrogens in high resolution HMNR?

A

Peaks are split into the number of neighbouring hydrogens +1 (n+1 rule)

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9
Q

What solvents are used in NMR?

A

CCl3, CDCl3, D2O

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10
Q

What does integration of HNMR tell us?

A

The proportion of the number of hydrogens in peak is due to. (Ratio of hydrogens in each environment)

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11
Q

What solvent must be used with esters and why?

A

CCl4 because it is non polar and esters do not dissolve in polar compounds

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12
Q

What is the mobile phase?

A

It is part which carries the soluble components of the mixture with it.

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13
Q

What is the stationary phase?

A

It is the part which will hold back the components in the mixture.

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14
Q

Why is TLC better than paper chromatography?

A

Faster
Small amounts used
Plates more robust than paper

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15
Q

What is the stationary phase in column chromatography?

A

Silica or alumina powder

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