Which compound matches the IR spectrum? 1,5-hexadiene dipropyl ether hexen-3-ol cyclohexane trans-4-octene 3-hexanol 1-methylcyclopentene
The Correct Answer and Explanation is:
The correct compound that matches the IR spectrum from the options provided is 1,5-hexadiene.
Explanation:
To identify the compound that matches an IR spectrum, we need to look for key functional groups and bond vibrations that would be indicated in the spectrum:
- 1,5-hexadiene:
- This compound contains a conjugated system of double bonds (C=C), which typically produces distinctive absorption peaks in the IR spectrum around 1650 cm⁻¹, indicative of the C=C stretch.
- The diene nature (two double bonds) will also likely result in weaker absorptions around 925-980 cm⁻¹ due to out-of-plane C-H bending vibrations.
- The C-H stretches in the alkane region will appear around 2850-3000 cm⁻¹.
- Dipropyl ether:
- This compound contains an ether functional group (-O-), which typically shows a strong C-O stretch around 1050-1150 cm⁻¹. It does not have conjugated double bonds, so it would not exhibit the typical peaks for alkenes or dienes.
- Hexen-3-ol:
- This compound contains both an alcohol (-OH) and a C=C double bond. The alcohol group would show a broad peak around 3200-3550 cm⁻¹ due to the O-H stretch, and the C=C stretch would appear around 1650 cm⁻¹. However, the IR spectrum might not have the same distinct features as 1,5-hexadiene due to the presence of the alcohol group.
- Cyclohexane:
- This is a saturated cyclic hydrocarbon, so its IR spectrum would primarily feature C-H stretches (around 2850-3000 cm⁻¹) and bending vibrations around 1450 cm⁻¹. It lacks any functional groups like double bonds or alcohols that would produce significant IR peaks.
- Trans-4-octene:
- The trans-alkene would have a C=C stretch around 1650 cm⁻¹, but the absence of conjugation and the different structure make this less likely to match the IR spectrum of 1,5-hexadiene.
- 3-hexanol:
- This alcohol would show a broad O-H stretch around 3200-3550 cm⁻¹ and a C-H stretch in the alkane region, but it does not have the conjugated system that would produce the unique features seen in 1,5-hexadiene.
- 1-methylcyclopentene:
- This compound has a C=C stretch around 1650 cm⁻¹, but the structure of a cyclopentene would produce different bending vibrations compared to the open-chain diene structure of 1,5-hexadiene.
Conclusion:
The presence of conjugated C=C double bonds in 1,5-hexadiene is the key feature that makes it the best match for the given IR spectrum. The IR peaks associated with conjugation and specific C-H bending patterns distinguish it from the other compounds.
