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How could IR spectroscopy distinguish between #CH_3CH_2CH_2OH# and #CH_3CH_2OCH_3#?

Answer 1

The IR spectrum of propan-1-ol would show a characteristic broad O-H stretching peak at 3200 to 3550 cm⁻¹. This peak would be absent in methoxyethane.

IR spectroscopy distinguishes compounds based on the vibrations of their bonds.

CH₃CH₂OCH₃ has C-C, C-H, and C-O bonds.

CH₃CH₂CH₂OH has C-C, C-H, C-O and O-H bonds.

So we look for the vibrational frequencies of an OH group.

The O-H group shows a characteristic broad stretching peak at 3200 to 3550 cm⁻¹.

The IR spectrum of propan-1-ol shows a broad peak centred at about 3350 cm⁻¹.

I couldn’t find a spectrum of methoxyethane, but the spectrum of methoxypropane, which should be similar, does not have this peak.

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Answer 2

Zoe Alexander

IR spectroscopy can distinguish between CH₃CH₂CH₂OH and CH₃CH₂OCH₃ based on their unique functional groups. CH₃CH₂CH₂OH contains an -OH (hydroxyl) group, which typically appears as a broad peak between 3200-3600 cm⁻¹ in the IR spectrum. CH₃CH₂OCH₃, on the other hand, contains an ether (-O-) group, which usually shows a sharp peak around 1100 cm⁻¹. Additionally, CH₃CH₂CH₂OH may exhibit peaks related to C-H stretching vibrations around 2800-3000 cm⁻¹, while CH₃CH₂OCH₃ may display peaks related to C-O stretching vibrations around 1000-1300 cm⁻¹. By analyzing the presence and position of these characteristic peaks in the IR spectrum, one can differentiate between the two compounds.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.