To determine which compound exhibits a sharp band at around \(3300 \text{ cm}^{-1}\) in the IR spectrum, we need to understand what specific functional groups give rise to absorption bands at this frequency.
The IR spectrum absorption around \(3300 \text{ cm}^{-1}\) is typically associated with the stretching vibrations of the -C≡C-H bond, found in terminal alkynes.
1,2-butadiene:
This compound has a chemical structure of \(\text{CH}_2=\text{C}=\text{CH}-\text{CH}_3\). The IR spectrum of 1,2-butadiene would exhibit absorption bands related to C=C stretching, but not near \(3300 \text{ cm}^{-1}\) as it lacks an alkyne functional group.
1,3-butadiene:
This compound, with a structure of \(\text{CH}_2=\text{CH}-\text{CH}=\text{CH}_2\), features conjugated double bonds and would exhibit typical alkene stretching frequencies, not at \(3300 \text{ cm}^{-1}\).
1-butyne:
1-butyne is \(\text{CH}_3-\text{C}\equiv\text{C}-\text{H}\), which contains a terminal alkyne group.
This compound is the correct answer as it contains the terminal alkyne (C≡C-H) that gives a characteristic sharp absorption band at approximately \(3300 \text{ cm}^{-1}\).
2-butyne:
2-butyne, \(\text{CH}_3-\text{C}\equiv\text{C}-\text{CH}_3\), has an internal alkyne and does not show the absorption at \(3300 \text{ cm}^{-1}\), as it lacks the terminal C-H bond needed to engage in this type of bonding interaction.
Conclusion: Given the IR spectral characteristics and the structures of the compounds, 1-butyne is the correct answer as it exhibits a sharp band at around \(3300 \text{ cm}^{-1}\) due to the presence of a terminal alkyne group.
Important Questions from IR Spectroscopy
In an IR spectra of 1-octyne and 4-octyne, the IR-spectra of 4-octyne does not have C ≡ C stretch absorption peak. The reason for this observation is that _________.
An IR-spectra is found to have a medium adsorption peak near 3400cm-1. This corresponds to which organic compound?
The number of CO bands for isomers from sets (i) and (ii) in their IR spectra
Set (i): Trigonal bipyramidal isomers, axial‐Fe(CO)4L (A)and equatorial‐Fe(CO) 4 L(B)
Set (ii): Octahedral isomers, fac‐Mo(CO)3L3 (C) and mer‐Mo(CO)3L3(D)
are
Match List I with List II
List I
List II
functional groups
respective approximate symmetric and asymmetric stretching frequencies
A.
N - H bonds of R - NH2
I.
1790 and 1810
B.
N - O bonds of R - NO2
II.
3300 and 3400
C.
C = O bonds of anhydride
III.
1350 and 1550
Choose the correct answer from the options given below:
The molecule that can absorb in the infra-red among the following is
