IR: Carbonyl Compounds Strong, sharp C=0 peak 1670 to 1780 cm- Exact absorption characteristic of type of carbonyl compound 1730 cm-I in saturated aldehydes 1705 cm-l in aldehydes next to double bond or aromatic ring 0 0 Aldehydes CH3CH2CH CH3CH=CHCH H 1730cm-1 1705cm-1 1705cm-1 Thomson· Brooks Col
IR: Carbonyl Compounds • Strong, sharp C=O peak 1670 to 1780 cm-1 • Exact absorption characteristic of type of carbonyl compound – 1730 cm-1 in saturated aldehydes – 1705 cm-1 in aldehydes next to double bond or aromatic ring
C=O in Ketones 1715 cm-l in six-membered ring and acyclic ketones 1750 cm-l in 5-membered ring ketones 1690 cm-l in ketones next to a double bond or an aromatic ring 0 0 Ketones CH3CCH3 CH3CH=CHCCH3 1715cr 1690cm Thomson· Brooks cole 1690
C=O in Ketones • 1715 cm-1 in six-membered ring and acyclic ketones • 1750 cm-1 in 5-membered ring ketones • 1690 cm-1 in ketones next to a double bond or an aromatic ring
C=O in esters 1735 cm-l in saturated esters 1715 cm-l in esters next to aromatic ring or a double bond 0 Esters CH CoCH CHCH=chcoCh OCH3 1735cm 1715cm 1715cm Thomson· Brooks cole
C=O in Esters • 1735 cm-1 in saturated esters • 1715 cm-1 in esters next to aromatic ring or a double bond
13. 3 Ultraviolet spectrum E nergy Ultraviolet Vacuum nEar Infrared ultraviolet 5 infrared A=2×10 A=4×10-m =200nm =400nm i=5×104cm =25×104cm-1
13.3 Ultraviolet Spectrum
Example: 1, 4-butadiene has four T molecular orbitals with the lowest two occupied Electronic transition is from homo to lumo at 217 nm(peak is broad because of combination with stretching, bending) y3 LUMO T 目++++ UV irradiation Four p atomic HOMO orbitals Ground-state Excited-state electronic electronic configuration configuration Thomson· Brooks cole
• Example: 1,4-butadiene has four p molecular orbitals with the lowest two occupied • Electronic transition is from HOMO to LUMO at 217 nm (peak is broad because of combination with stretching, bending)