Mid-IR Flashcards
How does IR spectroscopy work?
This is a generalization
“MIR spectroscopy relies on light absorption. Incident IR light upon a sample causes biochemical bonds to vibrate. Vibrational modes of molecule thereby cause specific amounts of energy from the incident IR beam to be absorbed, reducing the intensity of the subsequently detected IR beam.”
Vibrational Spectroscopy for Plant Varieties and Cultivars Characterization
Paul Skolik, … Francis L. Martin, in Comprehensive Analytical Chemistry, 2018
2.1 Mid-Infrared Spectroscopy
What does it mean if an IR band appears at a relatively higher wavenumber (cm-1) than another IR band.
Because wavenumber and frequency/energy are directly proportional, the IR band at a higher wavenumber is oscillating at a higher frequency/energy than an IR band found a t lower wavenumbers.
Which IR band appears at a higher wavenumber: free vs, H-bonded -OH stretching?
Also, what other prominent differences are there between these two?
H-Bonded -OH IR bands are perhaps the most common, given a characteristically broad band at around 3200-3550 cm-1. Whereas, free -OH IR bands are sharp and absorb at higher wavenumbers (up to 3800 cm-1).
The sp3 and sp2 C-H stretching bands occur relatively close together on the IR spectrum. Where are they located and which is the higher wavenumber?
sp3 and sp2 C-H stretching bands can be found at ~2900 cm-1 and ~3100 cm-1, respectively. If you think about the bonding strength of a double vs. single bonded carbon, this seems intuitive, since it would require more energy to vibrate the C-H bond of a double-bonded carbon.
What is the characteristic wavenumber for the C=O stretch of an anhydride?
The carbonyl stretching bands for an anhydride produces two signals, one at ~1800 cm-1 and the other at ~1750 cm-1
What is the characteristic wavenumber for the C=O stretch of an acid chloride (acyl chloride)?
The carbonyl stretching bands for an acy chloride produces a signal at ~1800 cm-1
What is the characteristic wavenumber for the C=O stretch of an aldehyde?
The C=O stretching frequency of an aldehyde produces an intense, sharp IR band at ~1710 cm-1
What is the characteristic wavenumber for the C=O stretch of an ester?
The C=O stretching frequency of an ester produces an intense, sharp IR band at ~1735 cm-1
What is the characteristic wavenumber for the C=O stretch of a ketone?
The C=O stretching frequency of a ketone produces an intense, sharp IR band at ~1710 cm-1
What is the characteristic wavenumber for the C=O stretch of a carboxylic acid?
The C=O stretching frequency of a carboxylic acid produces an intense, sharp IR band at ~1710 cm-1
What is the characterisitic wavenumber for the C=O stretch of an amide?
The C=O stretching frequencye of an amide produces an intense, sharp IR band at ~1660 cm-1
What wavenumber of the IR spectrum would you expect to see the C=C stretch for an alkene?
The C=C stretching frequency can be found at ~1600 cm-1
From the list of given molecules, identify which would produce the following IR spectrum:
Authored by William Reusch, minor edits have been made for clarity to suit the flashcard format.
From the list of given molecules, identify which would produce the following IR spectrum:
Authored by William Reusch, minor edits have been made for clarity to suit the flashcard format.
From the list of given molecules, identify which would produce the following IR spectrum:
Authored by William Reusch, minor edits have been made for clarity to suit the flashcard format.
From the list of given molecules, identify which would produce the following IR spectrum:
Authored by William Reusch, minor edits have been made for clarity to suit the flashcard format.
