Question

CHEM 266- Homewerk 3 Kese Peccer Name Bank the following compounds in order of increasing wavenumber for the carbonyl aboron your answer (2 pts) B NH2 As 2 Vou have performed the reaction below in the lab. List all the signals observed in the IR spectrum of the starting material and in the IR spectrum of the product. Explain how IR can be used to tell whether the reaction took place or not. CN NO2 MeO MeO NH2 IR vibrational signals (4 pts) Product Starting material Explain (2 pts) Page 1

Answer 1

1. D<B<C<A

This will be order of ketone wavenumber in increasing order as the structure of D where there is amine group along with conjugation in double bond. Amine group will pose +M effect and thus it will weakens C=O group and thus wavenumber decreases. In the structure of B there is conjugation of double bond and that is effect where ketone vibration decrease in wavenumber. Structure A will be having highest wavenumber due to absence of any unsaturation or substitution. C also have unsaturation but it is not alpha-beta unsaturation so wavenumber will be more than B but less than A.

2. IR Vibrational signals

Starting material	Product
Medium intensity peak near 3000cm-1 will be for C-H (alkane) streaching of ring	Strong streaching peak of N-H at 3300-3500 cm-1 will be there
weak intensity peak near 2900cm-1 will be for C-H (alkane) streatching of methyl group	weak intensity peak near 2900cm-1 will be for C-H (alkane) streatching of methyl group
strong peak near 1730cm-1 will be for C=O(carbonyl) streatching of aldehyde group	strong peak near 2250 cm-1 will be for CN streatching
strong peak near 1600cm-1 will be for NO2 streatching	Medium intensity peak near 1500 cm-1 will be for C=C (aromatic) streatching of ring
medium intensity peak near 1350 cm-1 will be for CH3 group bending	medium intensity peak near 1350 cm-1 will be for CH3 group bending
variable peak in the region of 1250-1050 cm-1 will be there for ether C-O-C streatching of ether	variable peak in the region of 1250-1050 cm-1 will be there for ether C-O-C streatching of ether

Explanation: There will be some common vibrations and some different. There is aldehyde and NO2 group in starting material which vibration won't be in the product. But the characteristics peak for amine, aromatic and cyano group will be found in product IR spectra.