IR plastics

Question 1

Why does C-O have a higher wavenumber than C-Cl?

Answer 1

C-Cl has a larger mass, and mass is inversely proportional to wavenumber. Therefore the large mass = low wavenumber

Question 2

Why does C=O have a larger wavenumber than C-O?

Answer 2

Higher bond order means higher energy, energy is proportional to wavenumber

Question 3

Wavenumber is proportional to

Answer 3

Energy, frequency, dipole moment

Question 4

Wavenumber is inversely proportional to

Answer 4

wavelength and mass

Question 5

All materials are

Answer 5

different in their atomic, molecular, and bonding compositions

Question 6

What are polymers

Answer 6

macromolecules (large molecules) made up of monomers

Question 7

what are monomers?

Answer 7

repeating units

Question 8

what does n mean?

Answer 8

the number of monomers in a polymer

Question 9

PETE

Answer 9

Polyethylene Terephthalate

Question 10

HDPE

Answer 10

High Density Polyethylene

Question 11

PVC/V

Answer 11

Polyvinyl chloride

Question 12

LDPE

Answer 12

Low Density Polyethylene

Question 13

PP

Answer 13

Polypropylene

Question 14

PS

Answer 14

Polystyrene

Question 15

Types of molecular vibrations

Answer 15

Stretches and bends

Question 16

Types of stretches

Answer 16

Asymmetric and Symmetric

Question 17

Types of bends

Answer 17

In or out of plane and scissor

Question 18

Mixture of different polymers

Answer 18

Polymer blend

Question 19

X-Ray Photoelectron Spectroscopy (XPS)

Answer 19

identifies the surface chemistry of different plastics including colour and width.

ie. a black plastic would be indecipherable in IR

Question 20

Infrared Spectroscopy (IR)

Answer 20

identifies the functional groups of polymers, meaning it can differentiate between plastics of the same family (Polyethylene)

Question 21

If a peak is found at a higher wavenumber what does that mean?

Answer 21

that it represents a higher energy dipole bond

Question 22

What does the wavenumber of absorbed light depend on?

Answer 22

the atom’s bonding environment (dipoles, bond order, vibration, type of atoms etc)

Question 23

IR light detects what?

Answer 23

wavelengths that are absorbed and or transmitted

Question 24

Region left of the peak

Answer 24

the functional group region, useful to analyzing specific bonds in unknown structures

Question 25

Region right of the peak

Answer 25

the fingerprint region, unique to every molecule

Question 26

sp², C-H stretch

Answer 26

3000-3100

Question 27

sp³, C-H stretch

Answer 27

2840-3000

Question 28

CH3 Bend

Answer 28

1350-1475

Question 29

CH2 bend

Answer 29

1450-1475

Question 30

C=O stretch

Answer 30

1650-1770

Question 30

C=C ring pair stretch

Answer 30

1400-1500 and 1585-1600

Question 31

C-O stretch

Answer 31

1200-1310

Question 32

C-Cl stretch

Answer 32

550-850

Question 33

O-H stretch

Answer 33

3000 - 3300

usually very broad and weak

Question 34

Type of IR used during this experiment

Answer 34

ATR-IR

Question 35

How do you calculate the amount of light absorbed

Answer 35

measuring intensity of light entering crystal and intensity of light reaching the detector

Question 36

Why does a sp³ occur at lower wavenumbers than sp²?

Answer 36

The double bond of the sigma framework of sp2 requires more energy to break/vibrate bc it has more s character which leads to shorter and stronger bonds.

Question 37

Why does the acetate ion only have a peak at 1400?

Answer 37

Because of the C-H bend that is there (sp^3), because the acetate ion looses the H ion that allows it to vibrate so it vibrates less and the C-O bond is completely eliminated

Question 38

Can IR distinguish well between LDPE and HDPE?

Answer 38

To a certain extent bc one certain peak, but there are other ways that do it better

differential scanning calorimetry (DCS) works better because they use physical properties

Question 39

Difference between LDPE and HDPE

Answer 39

LDPE has an “R” group, limiting its bonds with other monomers, leading to a linear structure that is flexible

HDPE is a long branching chain of monomers that can pack together, making it firmer and rigid.