Ultraviolet and Infrared Spectroscopy

Question 1

What is required for absorption of electromagnetic radiation to occur in a molecule?

Answer 1

The energy of the photon must match the difference between two energy states in the molecule (ground state to excited state)

Question 2

The larger the energy difference between two states-

Answer 2

the higher the energy of radiation needed for absorption

Question 3

Higher energy light (UV-visible) causes

Answer 3

electronic excitation

Question 4

Lower energy radiation (infrared) causes

Answer 4

vibrational excitation

Question 5

What bonds absorb at a wavelength of between 4000-2500

Answer 5

Bonds to hydrogen (C-H, O-H, N-H)

Question 6

What bonds absorb at a wavelength of 2500-2000

Answer 6

Triple bonds

Question 7

What bonds absorb at a wavelength of 2000-1500

Answer 7

Double bonds

Question 8

What bonds absorb at a wavelength of 1500-400

Answer 8

Single bonds

Question 9

The higher the percent s-character-

Answer 9

the stronger the bond and the higher the wavelength of absorption

Question 10

What bonds in the IR spectrum absorb at around 3000-2850 cm-1

Answer 10

Csp3-H bonds (alkane)

Question 11

What bonds absorb at 3150-3000 cm-1

Answer 11

Csp2-H bonds (alkene, double bond)

Question 12

What bonds absorb at 3300 cm-1

Answer 12

Csp-H bonds (alkyne, triple bond)

Question 13

What compounds absorb at 1600, 1500

Answer 13

Benzene

Question 14

What molecules absorb at 3600-3300

Answer 14

Alcohols

Question 15

What molecules absorb at 3500 - 3300

Answer 15

Amine, N-H

Question 16

What bonds absorb at 2830-2700 IR

Answer 16

Aldehydes (Csp2-H)

Question 17

What functional group absorbs at 1730 IR

Answer 17

Aldehyde (C double bond O)

Question 18

What functional group absorbs at 1715 IR

Answer 18

Ketone (C double bond O)

Question 19

What functional group absorbs at 1745 - 1735

Answer 19

Ester (C doulbe bond O)

Question 20

What functional group absorbs at 1680-1630 IR

Answer 20

Amide (C double bond O) (N-H at 3400 - 3200)

Question 21

What functional group aborbs at 3500-2500 (O-H) and 1710 (CdoublebondO)

Answer 21

Carboxylic acid

Question 22

What functional group absorbs at 2250

Answer 22

Nitrile (ctriple bondN)

Question 23

What are the two main uses of UV Spectroscopy

Answer 23

Measure at one wavelength and record full spectrumm

Question 24

The Beer-Lambert Law to calculate the relationship for the fraction of light absorbed on passage through a solution

Answer 24

log10(IncI/EmeI) = e x c x length = A
(IncI = Incident light intensity) (EmeI = emergent light intensity) (e = molar decadic extinction coefficient)

Question 25

The wavelength of violet

Answer 25

380 - 450

Question 26

Indigo

Answer 26

420-440

Question 27

Blue

Answer 27

450-495

Question 28

Green

Answer 28

495-570

Question 29

Yellow

Answer 29

570-590

Question 30

Orange

Answer 30

590-620

Question 31

Red

Answer 31

620-750

Question 32

Requires the use of potent vacuum pumps

Answer 32

MS

Question 33

Only detects ionised molecule

Answer 33

MS

Question 34

Is able to distinguish between isotopes and provides insight into their natural abundance

Answer 34

MS