UV / Visible Spectroscopy - Department of...

UV / Visible Spectroscopy

• UV wavelengths range from 200-400 nm

• Visible wavelengths range from 400-800 nm

• Energy absorbed causes electronic excitation

• σ, π, and n correspond to single bond, multiple bond, and nonbonded electrons, respectively

• absorptions correspond to transitions to antibonding orbitals.

• Energy absorbed causes electronic excitation

MO’s Involved in Transition

• A multitude of associated vibrational states lead to broad observed peaks, usually without fine structure.

Beer’s law:

A = • c •ε l

extinctioncoefficient

measuredabsorption

sampleconcentration

path lengthof sample cell

Experimental Setup

UV/Vis Spectrum

ε

400 blue red 800 λ(nm)

bathochromichypsochromic

hypochromic

hyperchromic λmax

Potential Compound Classes

• Polyenes

• Aromatic Compounds

• Compounds containing heteroatoms with non-bonded electrons.

• s-trans vs. s-cis

• substituent effects

Polyenes

253 nm217 nm

• Exhibit both π π* and n π* transitions

• Solvent effects

PolyenonesO

O

215 nm227 nm

• Some exhibit fine structure unlike polyenes

• Substituent effects often not large enough to distinguish functional groups or substitution patterns

Aromatics

UV Spectroscopy

• Utilize the tables in Crews and Pretsch to confirm the presence of certain functional groups by UV/Vis

• Useful as a detector for liquid-phase separation techniques

• This technique can be used to a limited extent to identify functional groups.

AzuleneNaphthalene

•Azulene is blue and naphthalene is colorless.

•Which compound has the largest λmax?

•Which compound has the smallest HOMO-LUMO gap?

Problem #1

O O

MgBr

Et2O

OH

Which compound(s) in this incomplete reaction will be invisible to an HPLC equipped with a UV detector operating

at 254 nm?

Problem #2

a

e cd b

1H NMR Spectrum

Problem #3

13C NMR Spectrum

z

y

x

w vu

171 173

92

70 eV EI Mass Spectrum

Br

NH2

H H

H

H

ae

d c

b

z

x

y

w

u

v

1H NMR Spectrum

1H

6H

1H

c

b

a

Problem #4

13C NMR Spectrum

z

y

x

LR CI Mass SpectrometryMeasured M+H 165.1±.05 by Chemical Ionization

H20 C3 N O4 PH25 N2 O S3H17 C7 O4H17 N6 O2 SH28 C P3 SH13 C8 N4H16 C4 N5 PH18 C N4 O3 PH19 N6 P2H15 C5 N3 O3H19 C2 N3 O3 SH26 C O2 P S2H15 C10 N OH18 C6 N2 O PH22 O7 PH21 C2 N3 O P2H13 C3 N6 O2H21 C4 O4 SH24 N O4 P SH21 C3 N2 O S2H27 N P4H24 C4 P3H23 C4 O2 P2H17 C2 N2 O6H11 C N9 OH17 C5 N4 SH26 N O2 P3H20 C N5 P SH19 C N5 S2H25 N O2 P2 SH22 C4 O2 P SH21 O9H15 N5 O5

H19 C7 N O SH22 C3 N2 O P SH23 N O4 S2H25 C O4 S2H20 C2 N3 O P SH17 C6 N2 O SH11 N11H17 C N4 O5H27 C O2 P2 SH21 C2 N4 S2H18 N6 P SH15 C4 N5 SH13 C2 N8 OH19 C3 N O6H21 C3 N O2 P2H18 C7 O2 PH29 C P4H23 C4 N O S2H26 N2 O P S2H19 C3 N O4 SH15 C4 N5 O2H19 C N4 O P2H18 N6 O2 PH16 C5 N3 O PH27 C P2 S2H13 C9 N2 OH17 C N4 O3 SH17 C6 N2 O3H23 O5 P2H20 C2 N3 O3 PH14 C3 N6 PH25 C O2 S3H11 C7 N5H23 N O6 S

H21 O7 SH27 C N O S3H22 C4 O4 PH18 C2 N2 O4 PH25 N O4 P2H15 C6 N O4H19 C N5 O2 SH26 N P3 SH23 C4 P2 SH15 C9 N3H18 C5 N4 PH16 N5 O3 PH21 C N5 P2H13 C4 N4 O3H21 C3 N2 O3 SH24 N O2 P S2H21 C4 O2 S2H17 C11 OH20 C7 N O PH23 C3 N2 O P2H17 C3 O7H11 C2 N7 O2H26 C O4 P SH19 C2 N3 O S2H22 C3 N P3H19 C7 P2H15 C N3 O6H9 N10 OH19 C6 N3 SH28 C O2 P3H22 C2 N4 P SH17 N6 S2H140 C2H25 N2 O3 S2

H20 C3 N O2 P SH17 C7 O2 SH17 N6 O4H21 C8 O SH24 C4 N O P SH27 N2 O P2 SH18 C N4 O P SH24 O3 P3H15 C5 N3 O SH13 C N10H19 C2 N3 O5H26 C P S3H23 C3 N3 S2H22 O5 P SH13 C3 N6 SH15 C3 N7 OH21 C4 O6H19 C2 N2 O2 P2H24 N O6 PH16 C6 N O2 PH13 C10 O2H25 C5 O S2H28 C N O P S2H17 C2 N2 O4 SH17 C5 N4 O2H17 N5 O P2H20 C N5 O2 PH14 C4 N4 O PH25 N P2 S2H11 C8 N3 OH22 C4 P S2H15 N5 O3 SH19 C7 N O3H27 N3 S3

H22 C3 N2 O3 PH18 C3 O5 PH12 C2 N7 PH23 N O2 S3H9 C6 N6H19 N7 O SH25 C O6 SH29 C2 O S3H16 C N3 O4 PH27 C O4 P2H13 C5 N2 O4H21 C2 N4 O2 SH21 C3 N P2 SH17 C10 N2H18 C7 P SH20 C6 N3 PH23 C2 N4 P2H11 C3 N5 O3H23 C4 N O3 SH26 N2 O3 P SH19 C3 N O2 S2H25 O P4H22 C8 O PH25 C4 N O P2H15 C2 N O7H9 C N8 O2H28 N2 O P3H17 C N4 O S2H23 O3 P2 SH20 C2 N2 P3H25 C S4H23 N O8H17 C6 N P2H13 N4 O6

H21 C7 N2 SH14 C10 PH24 C3 N3 P SH21 O5 S2H138 C NH27 C N O3 S2H18 C2 N2 O2 P SH15 C6 N O2 SH19 C N5 O4H26 C5 O P SH29 C N O P2 SH16 N5 O P SH13 C4 N4 O SH15 C2 N9H21 C3 N2 O5H19 C3 O3 P2H24 N P S3H21 C4 S3H25 C4 N2 S2H28 N3 P S2H17 C3 O5 SH11 C2 N7 SH17 C4 N6 OH17 C N3 O2 P2H20 N7 O PH26 C O6 PH14 C5 N2 O2 PH11 C9 N O2H30 C2 O P S2H15 C N3 O4 SH19 C6 N3 O2H22 C2 N4 O2 PH12 C3 N5 O PH9 C7 N4 O

H25 N2 O5 SH20 C3 N P S2H17 C7 S2H21 C8 O3H29 C N2 S3H24 C4 N O3 PH16 C2 N O5 PH10 C N8 PH27 N2 O3 P2H13 C6 O5H7 C5 N7H21 C N6 O SH24 O P3 SH14 N4 O4 PH11 C4 N3 O4H23 C3 N3 O2 SH22 O3 P S2H19 C2 N2 P2 SH19 C11 NH16 C6 N P SH22 C7 N2 PH13 C10 SH25 C3 N3 P2H9 C2 N6 O3H25 C5 O3 SH28 C N O3 P SH17 C2 N2 O2 S2H148 OH20 C3 O P3H27 C5 O P2H13 C N2 O7H7 N9 O2H30 C N O P3H15 N5 O S2

H27 N3 O2 S2H18 C3 O3 P SH18 C N3 P3H23 N S4H19 N7 O3H25 C O8H15 C5 N2 P2H23 C8 N SH12 C9 N PH26 C4 N2 P SH9 C13H136 N2H29 N3 P2 SH29 C2 O3 S2H16 C N3 O2 P SH13 C5 N2 O2 SH21 C2 N4 O4H31 C2 O P2 SH11 C3 N5 O SH17 C3 N8H23 C4 N O5H17 C2 N O3 P2H26 N2 O5 PH14 C6 O3 PH19 C3 N S3H27 C5 N S2H30 C N2 P S2H15 C2 N O5 SH9 C N8 SH19 C5 N5 OH15 N4 O2 P2H22 C N6 O PH12 C4 N3 O2 PH23 O P2 S2

H9 C8 N2 O2H13 N4 O4 SH21 C7 N2 O2H24 C3 N3 O2 PH10 C2 N6 O PH21 O3 S3H7 C6 N5 OH21 N8 SH27 C N O5 SH18 C2 N2 P S2H15 C6 N S2H31 C2 N S3H26 C5 O3 PH14 C N2 O5 PH8 N9 PH29 C N O3 P2H11 C5 N O5H5 C4 N8H23 C2 N5 O SH19 C3 O P2 S

HR CI Mass Spectrometry

Measured M+H 165.1130±.002 by Chemical Ionization

Deviation-0.029543-0.602715-1.9136592.237752-3.2853866.1860548.070170-8.1614539.954286

Mass165.112995165.112900165.112684165.113369165.112458165.114021165.114332165.111652165.114644

FormulaH20 C3 N O4 P H25 N2 O S3 H17 C7 O4 H17 N6 O2 S H28 C P3 S H13 C8 N4 H16 C4 N5 P H18 C N4 O3 P H19 N6 P2

O

O

O

O

H

H

H

b

c

a

zyx

UV / Visible Spectroscopy - Department of...

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