IR Spectroscopy:

Question 1

IR spectroscopy relies on the simple observation that chemical bonds behave like….?

Answer 1

springs.

Question 2

In what two ways can a bond stretch in what two ways?

Answer 2

Symmetrical and Asymmetrical.

Question 3

What energy corresponds to getting a molecule to vibrate?

Answer 3

heat or infrared energy.

Question 4

What are all the ways a molecule can vibrate?

Answer 4

stretching: symmetrically or asymmetrically.
bending: Scissoring, rocking, wagging, twisting

Question 5

What does scissoring look like, in terms of molecular vibration?

Answer 5

substients getting close to the middle.

Question 6

What does rocking look like, in terms of molecular vibration?

Answer 6

the substients have moved into a right angle.

Question 7

What does wagging look like, in terms of molecular vibration?

Answer 7

both substients on wedges.

Question 8

What does twisting look like, in terms of molecular vibration?

Answer 8

a wedge and a dashed substient.

Question 9

Bond stretches require (higher/lower) infrared energies to occur and appear at higher frequencies?

Answer 9

Higher.

Question 10

Bond Bends at (higher/lower) infrared energies to appear at lower frequiences?

Answer 10

lower.

Question 11

Stronger bonds stretch at (higher or lower) frequencies than weaker bonds?

Answer 11

• Higher

Question 12

The heavier the atoms connected by a chemical bond, the (higher or lower) the frequency at which the bond will stretch?

Answer 12

• Lower.

Question 13

What are the three regions on the infrared spectrum of heat causing molecular vibration?

Answer 13

1. ) functional region: all organic functional groups reside here (4,000 cm -1550)
2. ) Structural region: certain diagnostic C-H bending vibrations are found here (1000-600)
3. ) Finger print region: 1550 - 1000 cm: contains a large number of vibrations:

Question 14

What is the frequency of an alkane stretch?

Answer 14

3,000-2,850 cm^-1

Question 15

What is the frequency of an CH3 bend?

Answer 15

1450 & 1375

Question 16

What is the frequency of an alkene stretch?

Answer 16

3100 - 3000

Question 17

What is the frequency in which alcohols, Ethers, esters, carboxylic acids & anhydrides reside?

Answer 17

1300-1000

Question 18

What is the frequency in which alcohols & phenols reside? and what range do carboxylic acid resides?

Answer 18

alcohols and phenols: 3650-3200

Carboxylic acids: 3400-2400

Question 19

What are the frequency ranges in which alcohols can appear?

Answer 19

1300-1000
&
3650-3200