Question #5f295

1 Answer
Nov 18, 2017

Here's what I get.

Explanation:

1) Phenol and hexan-1-ol

Both compounds have #"-OH"# groups, so both will show strong, broad absorptions in the #"3300 cm"^"-1"# to #"3400 cm"^"-1"# region.

But phenol has unsaturated #"C=C"# and #"=C-H"# bonds, while hexan-1-ol has only saturated #"C-C"# and #"C-H"# bonds.

Phenol will show characteristic absorptions at

  • #"3030 cm"^"-1"# ( aromatic #"C-H"# stretch)
  • #"1600 cm"^"-1"# and #"1500 cm"^"-1"# (aromatic #"C=C"# stretch)
  • #"750 cm"^"-1"# and #"700 cm"^"-1"# (aromatic #"C-H"# bend)

Phenol
(From webbook.nist.gov)

Hexan-1-ol has none of these characteristic absorptions.

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2) Hexane and cyclohexane

Here the difference is more subtle: hexane has methyl groups but cyclohexane doesn't.

Thus, we expect to see #"CH"_3# vibrations in hexane but only #"CH"_2# vibrations in cyclohexane.

The main difference is that #"CH"_2# groups have bending vibrations at about #"1460 cm"^"-1"# but #"CH"_3# groups have bending vibrations at both #"1460 cm"^"-1"# and #"1380 cm"^"-1"#

Compare the two spectra. Do you see the extra absorption band at #"1380 cm"^"-1"# in the spectrum of hexane?

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