Place your responses to each of the following questions in the appropriate boxes
ID: 891011 • Letter: P
Question
Place your responses to each of the following questions in the appropriate boxes on the Spectroscopy II Pre-lab Answer Sheet. The Pre-lab Answer Sheet is due when you arrive in lab to do the Spectroscopy II lab. You do not need to turn in this sheet with your answers. For each of the following compounds, give the number of signals (resonances) that you would expect to find in the 13C NMR spectrum For each of the following compounds, give the approximate frequency (in reciprocal centimeters, cm- 1) of two diagnostic peaks you would expect to find in the infrared (IR) spectrum. Be sure to also give the bond responsible for the peak. For each of the following, give two possible bonds that could be responsible for the indicated peak in an infrared spectrum. 2235 cm-1 1450 cm-1Explanation / Answer
Answer – 1)We need to determine the how many signal give each egiven compound in 13CNMR spectra –
a)Benzene – It has no any substituent and all carbons are equivalent in nature, so it gives only one signal in 13CNMR.
b) In this one there are total 6 C and in that two are same, so total number of signals are 5
c) In this one there is given benzene ring with two methyl group at meta to each other, so total 8 carbon and in that and there are 3 signal with 6 C and two are different, so total number of signals are 5
d) In this one there are 8 carbon with benzene ring and substituted –NO2 and –COOCH3, so all are different type of C, so total number of signals are 8
2) In this one we need to look for the IR stretching frequency for each given compound
a) In this one given normal ketone, so IR frequency for C=O is at in between 1710 to 1730 cm-1, for C-H it is near to 3200 cm-1
b) In this one we are given aldehyde and there is IR frequency for C=O is at in between 1730 to 1750 cm-1 and O=C-H at 2730 and 2830 cm-1
c) In this one we are given alkyne and the IR frequency for C triple bond C is at in between 21500 to 2200 cm-1 and the C-H at 3300 cm-1
d) In this one given is primary alcohol, so the IR frequency for –O-H at in between 3200 to 3500 cm-1 with strong and broad and for C-O it is at 1100 to 1150 cm-1.
3) a) At 2235 cm-1 there is possibility of alkyne –C triple bond C- and another is for –C triple bond N means for cyanide
b) 1450 cm-1 for the alkane C-H bending and it is maybe for N-O in nitro.