IR Spectroscopy: Flashcards
IR spectroscopy relies on the simple observation that chemical bonds behave like….?
springs.
In what two ways can a bond stretch in what two ways?
Symmetrical and Asymmetrical.
What energy corresponds to getting a molecule to vibrate?
heat or infrared energy.
What are all the ways a molecule can vibrate?
stretching: symmetrically or asymmetrically.
bending: Scissoring, rocking, wagging, twisting
What does scissoring look like, in terms of molecular vibration?
substients getting close to the middle.
What does rocking look like, in terms of molecular vibration?
the substients have moved into a right angle.
What does wagging look like, in terms of molecular vibration?
both substients on wedges.
What does twisting look like, in terms of molecular vibration?
a wedge and a dashed substient.
Bond stretches require (higher/lower) infrared energies to occur and appear at higher frequencies?
Higher.
Bond Bends at (higher/lower) infrared energies to appear at lower frequiences?
lower.
Stronger bonds stretch at (higher or lower) frequencies than weaker bonds?
- Higher
The heavier the atoms connected by a chemical bond, the (higher or lower) the frequency at which the bond will stretch?
- Lower.
What are the three regions on the infrared spectrum of heat causing molecular vibration?
- ) functional region: all organic functional groups reside here (4,000 cm -1550)
- ) Structural region: certain diagnostic C-H bending vibrations are found here (1000-600)
- ) Finger print region: 1550 - 1000 cm: contains a large number of vibrations:
What is the frequency of an alkane stretch?
3,000-2,850 cm^-1
What is the frequency of an CH3 bend?
1450 & 1375
