Question

Which compound matches the IR spectrum? 1-hexen-3-ol 1-methylcyclopentene 3-hexanol 1.5-hoxadiene cylohexane trans-4-octene dipropyl ether Which compound matches the IR spectrum? cyclohexane dipropyl ether 1-hexen-3-ol 1.5-hoxadiene 3-hexanol trans-4-octene 1-methylcyclopentene Which compound matches the IR spectrum? dipropyl ether cyclohexane 1.5-hexadiene trans-4-octene 3-hexanol 1-hexen-3-ol 1-methylcyclopentene

Answer 1

Concepts and reason

IR spectrum is an analysis of the interaction of molecule with infrared radiation. IR spectra help to identify the different functional groups present in a compound.

Fundamentals

Infrared spectroscopy:

Infrared bands appear at the certain absorption frequencies.

Reduced mass and spring constant of a bond changes according to the function group. Stronger bonds with lighter atoms are having higher frequency range. Different functional group gives absorption band at different range and intensity in IR. By knowing the absorption range, predict the functional group present in the given molecule. The table shown below gives the IR absorption of the common functional groups.

These groups absorb the IR radiation since their bonds are polar, which makes the bonds to vibrate at a particular wavenumber, and by using the wave numbers, different functional groups can be identified in the IR spectra.

Functional group	Range of absorption
Alkane	2800-2900
Alcohol	3400-3600
Alkene$(C=C) $ $(C=C-H) $	1640-1680 3020-3100
Alkyne$(C=C) $ $(C=C-H) $	2100-2250 3300
Nitrile$(C=N) $	2200-2250
Aromatics	1650-2000
Amines	3300-335
Carbonyls$(C=0) $ Aldehyde Ketone Ester Acid	1720-1690 1750-1680 1750-1735 1780-1710

The given IR spectrum contains two bands.

Peak at indicates the Alkyl bond and peak at indicates the alkyl bond.

Peaks at and another is at $1600cm*(C=C) $ .

This compound shows peaks at$3000cm*(C=C-H), $

Peak near at

This compound contains three peaks. Peaks are given below:

Three peaks are present in the cyclohexane at

Trans -4-octene has two functional groups that is alkene$(C=C) $at and $(C=C-H) $at

This compound shows peaks at

Wrong options are 3- hexanol, 1-hexen-3-ol, dipropyl, 1-methylcylcopente, 1,5-hexadiene,and trans-4-octene.

Cyclohexane is correct option.

In given IR spectrum contains two bands.

Peak at 2900-2800cm^-1 indicates the Alkyl bond and peak at 1100 cm^-1 indicates the bond.

Three peaks are present in the cyclohexane at

This compound shows peaks at

.

Peaks at and another peak is at .

This compound contains three peaks. Peaks are given below:

Peak near at

Trans -4-octene has two functional groups that is alkeneat and at

This compound shows peaks at

Wrong options are cyclohexane, 1-hexen-3-ol, 1,5-hexadiene, 3- hexanol, trans-4-octene, and 1-methylcylcopente.

Dipropyl ether is the correct option.

The given IR spectrum contains broad peak at which indicates the group indicates the stretch of ^, and indicates the stretch.

This compound shows peaks at

Three peaks are present in the cyclohexane at

This compound contains three peaks. Peaks are given below:

Trans -4-octene has two functional groups that is alkeneat and at

Peak near at

Peaks at and another peak is at .

This compound shows peaks at

Wrong options are dipropyl ether, cyclohexane, 1,5-hexadiene, trans-4-octene, 3- hexanol, 1-hexen-3-ol, and 1-methylcylcopente.

1-hexan-3-ol is the correct option.

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