Question

Assign the peak in the IR spectrum of dibenzalacetone that is at 1639 cm^-1. Is this...

Assign the peak in the IR spectrum of dibenzalacetone that is at 1639 cm^-1. Is this the normal absorption for this functional group? In benzaldehyde there is an absorption at 2738 cm^-1 but it is absent in the IR of dibenzalacetone. Why?

Science   Chemistry   
0 0
Add a commentTranscribed image text
Next >

Homework Answers

Answer #1

Benzylideneacetone is Ph-CH=CH-CO-CH=CH-Ph. The peak at 1639 cm-1 is the ketone C=O stretch of this compound is instead of the normal 1700 cm-1 is because of conjugation. The ketone of this molecule is highly conjugated through the double bond and into the aromatic ring. Hence the electrons of the ketone carbonyl are delocalized throughout the molecule and into the aromatic ring thus, lowering its observed IR wavenumber to 1639 cm-1.

The peak at 2738 cm-1 in benzaldehyde is due to aldehydic –C-H stretching. It is absent in Benzylideneacetone since it does not contain any aldehyde functional group.

0 0
Know the answer?
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Log In

Sign Up

Not the answer you're looking for?
Ask your own homework help question
Similar Questions
) Obtain the IR spectrum for anthracene.   Draw the structure of anthracene on the IR spectrum...
) Obtain the IR spectrum for anthracene.   Draw the structure of anthracene on the IR spectrum and identify the absorption signals for aromatic C=C and aromatic C-H directly on the IR spectrum. b) Obtain the IR spectrum of Maleic Anhydride. Draw the structure of maleic anyhydride    on the IR spectrum and identify the absorption signals for C=C and C=O directly on he IR spectrum. c) Obtain the IR spectrum of your product.   Draw your product on the spectrum and identify...
A peak observed at 1690 cm-1 in the mid-IR spectrum of guanine is assigned to the...
A peak observed at 1690 cm-1 in the mid-IR spectrum of guanine is assigned to the carbonyl stretching vibration What would be the peak position be if the 488 nm line from the argon-ion laser was used instead of the 514.5 nm line? Give you answer in both nm and in relative cm–1. What would the relative intensity of the peak be if the 488 nm line from the argon-ion laser was used instead of the 514.5 nm line? (Assume...
A compound, C9H12, shows an IR peak at 750 cm-1. Its 1H NMR spectrum has peaks...
A compound, C9H12, shows an IR peak at 750 cm-1. Its 1H NMR spectrum has peaks at delta 7.1 (4 H, broad singlet), 2.6 (2 H, quartet, J=8 Hz), 2.3 (3 H, singlet), and 1.2 (3 H, triplet, J=8 Hz). Draw its structure in the window below.
What is the fingerprint region of an IR spectrum? A.The region above 1500 cm-1 that contains...
What is the fingerprint region of an IR spectrum? A.The region above 1500 cm-1 that contains all of the distinguishable functional groups. B.The region of the IR that will allow us to positively identify a molecule because it is characteristic to that molecule C.The region below 1500 cm-1 that contains the majority of stretching and bending signals. D.Both A and B. E.Both B and C.
In comparison of IR spectrum between salicylaldehyde and salen H2, salicylaldehyde has a peak centred around...
In comparison of IR spectrum between salicylaldehyde and salen H2, salicylaldehyde has a peak centred around 1640 cm-1 while salen H2 has a peak around 1610 cm-1. Has it moved to higher or lower energy? What does this tell you about the strength of the C=O vs the C=N bond?
a) at approximately what location is the carbonyl peak of cyclohexanone on the IR spectrum? b)...
a) at approximately what location is the carbonyl peak of cyclohexanone on the IR spectrum? b) at approximately what location is the OH peak of cyclohexanol on the IR spectrum? c) is it jagged or rounded? d) what two classes of compounds can primary alcohols be oxidized? e) what determines which product results from such oxidation?
A compound, C10H14, shows an IR peak at 745 cm-1. Its 1H NMR spectrum has peaks...
A compound, C10H14, shows an IR peak at 745 cm-1. Its 1H NMR spectrum has peaks at delta 7.18 (4 H, broad singlet), 2.70 (4 H, quartet, J=7 Hz), and 1.20 (6 H, triplet, J=7 Hz). Draw its structure in the window below. You do not have to consider stereochemistry. You do not have to explicitly draw H atoms. In cases where there is more than one answer, just draw one.
Chemical Formula: C10H16O4. IR: Strong peak 1720 cm, peak at 1650 cm. Triplet (6H) at 1.1...
Chemical Formula: C10H16O4. IR: Strong peak 1720 cm, peak at 1650 cm. Triplet (6H) at 1.1 ppm, sextet (4H) at 1.7 ppm, triplet (4H) at 4.1 ppm, singlet (2H) at 6.5 ppm. What is the molecular structure?
The first line (peak) in the 12CO rotational spectrum is observed at 3.84235 cm-1 (corresponds to...
The first line (peak) in the 12CO rotational spectrum is observed at 3.84235 cm-1 (corresponds to the transition J-0 -> J-1). Calculate B, the rotational constant of 12CO (in cm-1). Calculate r, the link length of 12CO (in Armstrong) Calculate the position (the wave number, in cm-1) of the peak corresponding to the transition J-0 -> J-1 of 13CO. Molar masses (g/mol): 12C-12.00, 13C-13,0006, O-15.9994.
IR spectroscopy question: I have two shorter bumps at 3460 and 3309 cm -1 and I...
IR spectroscopy question: I have two shorter bumps at 3460 and 3309 cm -1 and I know this is supposed to be benzene? the product we were supposed to make in lab was 6-ethoxycarbonyl-3,5-diphenyl-2-cyclohexenone. If you could just go over the major functional groups and an estimation of where the absorptions should be for this molecule so I can compare it to my IR spectrum. Tried to put IR spectrum of my product up but it is blurry like every...
ADVERTISEMENT
Need Online Homework Help?

Get Answers For Free
Most questions answered within 1 hours.

Ask a Question
ADVERTISEMENT