Principles of Chemical Analysis ES (5)

Question 1

What is another name for the far UV region?

Answer 1

vacuum UV

Question 2

What is the far UV region’s wavelength limits?

Answer 2

less than 200 nm

Question 3

What are the energies involved in spectral transitions in far UV region?

Answer 3

greater than 50,000 cm-1

Question 4

What are the near ultraviolet regions wavelength limits?

Answer 4

200 - 400 nm

Question 5

What are the energies involved in the near UV spectral transitions?

Answer 5

50,000 - 25,000 cm-1

Question 6

What is the UV-A region?

Answer 6

315 - 4000 nm

Question 7

What is the UV-B region?

Answer 7

280-315 nm

Question 8

What is the UV-C region?

Answer 8

< 280 nm

Question 9

What are the wavelength limits of the visible region?

Answer 9

400 - 780 nm

Question 10

What are the energies involved in the spectral transitions in the visible region?

Answer 10

25,000 - 12,821 cm-1

Question 11

What is the range of molecular extinction coefficients seen in electronic spectra

Answer 11

5e5 for strongest to <1 for weakest

Question 12

What is the most probable electronic transition?

Answer 12

HOMO to LUMO

Question 13

What are the relative energy levels for the different types of transitions?

Answer 13

125 - 650 kJ/mol

Question 14

What type of bonds do σ bonds form

Answer 14

single

Question 15

what kind of bonds do pi electrons form

Answer 15

multiple

Question 16

what kind of bonds do n electrons form

Answer 16

nonbonding using atoms right of C on the table

Question 17

What is a chromophore?

Answer 17

group of atoms producing an electronic absorption

Question 18

What are auxochromophores?

Answer 18

substituents that increase intensity or wavelength of principle chromophores

Question 19

What are some of the typical auxochromophores?

Answer 19

methyl, hydroxyl, alkyl, halogen, amino groups

Question 20

What is bathochromic shift?

Answer 20

shift in absorption maximum to longer wavelength or lower energy (red shift)

Question 21

what is a hypsochromic shift?

Answer 21

shift in absorption maximum to shorter wavelength or higher energy (blue shift)

Question 22

What is a hyper chromic effect?

Answer 22

increase band intensity

Question 23

What is a hypochromic effect?

Answer 23

decrease in band intensity

Question 24

In what type of electronic transitions do σ-electrons take part?

Answer 24

σ to σ; n to σ; σ to pi*

Question 25

In what region the spectrum do σ transition occur?

Answer 25

outside the normal spectral range (far)

Question 26

In what type of electronic transitions do π-electrons take part?

Answer 26

σ to π*; π to π*; n to π*

Question 27

In what region of the spectrum do π transitions occur?

Answer 27

NEAR; alkenes 175 nm and alkynes 120 nm

Question 28

In what type of electronic transitions do n electrons take part?

Answer 28

n to σ*; n to π*

Question 29

In what region of the spectrum do these n transitions occur?

Answer 29

Near UV, far UV, vis

Question 30

What types of transitions do saturated hydrocarbons undergo?

Answer 30

σ to σ*

Question 31

What is the effect of unsaturation on electronic absorption spectra?

Answer 31

give rise to the most varied spectra

Question 32

What happens when functional groups containing n electrons are added tot eh molecule?

Answer 32

n to σ* allows for increased wavelength of σ to σ*

Question 33

What types of molecules demonstrate the most varied electronic spectra?

Answer 33

unsaturated