DEGREE OF UNSATURATION EXAMPLE

A COMPOUND HAS THE FORMULA C8H7Br

1. WORK OUT THE DEGREE OF UNSATURATION

2. PROPOSE A STRUCTURE FOR THE COMPOUND

Br

CH2

D.U. = 5

NORMAL MODES OF VIBRATION EXAMPLES

Symmetricalstretch

Asymmetricalstretch

Scissoring

Rocking Wagging Twisting

UV/VIS LECTURE EXERCISE

SUGGEST ALL POSSIBLE TRANSITIONS (e.g. n *) FOR THE FOLLOWING COMPOUND:

σ σ*

π π*

n σ*

n π*

d d

L M charge transfer

UV/VIS LECTURE EXERCISE

* transitions of the corrin ring

UV-VIS LECTURE EXERCISE

THE UV/VIS SPECTRUM OF A SOLUTION (conc. = 2.5 × 10-5 M) HAS TWO PROMINENT PEAKS.

THE FIRST AT 400 nm HAS AN ABSORBANCE OF 0.8, AND THE SECOND AT 550 nm HAS AN ABSORBANCE OF 0.1.

THE MEASUREMENT WAS CONDUCTED IN A CUVETTE WITH A PATHLENGTH OF 0.02 m.

CALCULATE THE EXTINCTION COEFFICIENT FOR BOTH PEAKS.

UV-VIS LECTURE EXERCISE cont.

A = ε×b×c

ε = A/(c × b)

ε400 = 0.8/(2.5 × 10-5 mol ℓ-1 × 2 cm)

= 16000 mol-1 ℓ cm-1

ε550 = 2000 mol-1 ℓ cm-1

TYPICAL INSTRUMENT

TYPICAL INSTRUMENT

Using only the peak integrals, assign which signals belong to which protons.

Using peak multiplicities, and prior knowledge about shielding, fully assign the 1H spectrum below.

A

A

B

B

C

C

D

D

HOW IS J CALCULATED?

THE MAGNITUDE OF J CAN BE CALCULATED BY × THE

SEPARATION OF THE LINES IN δ (ppm) UNITS BY THE

RESONANCE FREQUENCY OF THE SPECTROMETER IN MHz.

J (Hz) = δ (ppm) × ν0 (MHz)

ab

Jba

Jba

Jab

IF Ha AND Hb ARE COUPLED, THEN THE SPACING BETWEEN THE LINES ARE EQUAL, AND Jab

= Jba

MORE ON J

Jab = Jba = 6.0 Hz