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CHY1402 - Analytical methods and applications > IR and UV spec > Flashcards

IR and UV spec Flashcards

1
Q

What is the order of the frequency values for carbonyl compounds from lowest to highest?

A 
Amide 
Carboxylic acid
Ketone 
Aldehyde
Ester 
Anhydride 
Acid chloride 
Anhydride
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2
Q

What are the electron withdrawing effects in carbonyl compounds?

A

Electron withdrawing group tends to draw electrons into the c=o bond which strengthens the bond and increases the frequency

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3
Q

What is the resonance effect in carbonyl compounds?

A

unpaired electron on nitrogen conjugates with C=O

If there is more single bond character, lowers frequency

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4
Q

What is the wavelength for the UV vis spec?

A

190nm to 800nm

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5
Q

What governs which transitions are observed?

A

The selection rules

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6
Q

What is the beer-lambert law equation?

A

A = e C l

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7
Q

What orbital transitions are seen in R-OH? What is the typical e value?

A

n - > sigma star

300 M-1 cm-1

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8
Q

What orbital transitions are seen in R-O-R? What is the typical e value?

A

n - > sigma star

3000 M-1 cm-1

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9
Q

What orbital transitions are seen in R-SH? What is the typical e value?

A

n -> sigma star

1000 M-1 cm-1

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10
Q

What orbital transitions are seen in R-NO2? What is the typical e value?

A

n -> pi star

<10 M-1 cm-1

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11
Q

What is the hyper chromic effect?

A

Increase in absorbance

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12
Q

What is the hypo chromic effect?

A

Decrease in absorbance

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13
Q

What is the bathochromic shift? (red shift)

A

The shift to a longer wavelength

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14
Q

What is the hypsochromic shift? (blue shift)

A

The shift to a shorter wavelength

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15
Q

Why does the hyper chromic effect occur?

A

Introduction of an auxochrome usually increases the intensity of absorption

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16
Q

Why does the hypo chromic effect occur?

A

Introduction of methyl group distorts the geometry of the molecules which causes the effect

17
Q

Why does the bathochromic shift occur?

A

Due to the presence of an auxochrome or by the change of polarity of solvent

18
Q

Why does the hypsochromic shift occur?

A

Due to the removal of conjugation or by the change of the polarity of the solvent

19
Q

What is an auxochrome?

A

a group which does not itself act as a chromophores but whose presence brings about a change in the absorption
They are a colour enhancing group

20
Q

What is a chromophore?

A

Any isolated covalently bonded group that shows a characteristic absorption in the ultraviolet or visible region

CHY1402 - Analytical methods and applications (14 decks)

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