Functional Groups and IMFs

Question 1

R—OH

Answer 1

alcohol

Question 2

R—Cl

Answer 2

Alkyl halide

Question 3

R—NH2

Answer 3

Amine

Question 4

R2C—CR2
\ /
O

Answer 4

Epoxide

Question 5

R—O—R

Answer 5

Ether

Question 6

RC≡N

Answer 6

Nitrile

Question 7

R—NO2

Answer 7

Nitroalkane

Question 8

R—S—R

Answer 8

Sulfide

Question 9

R—SH

Answer 9

Thiol

Question 10

. O
||
R—CH

Answer 10

Aldehyde

Question 11

. O
||
R—C—R

Answer 11

Ketone

Question 12

. O
||
R—C—OH

Answer 12

Carboxylic acid

Question 13

. O
||
R—CX

Answer 13

Acyl halide

Question 14

. O O
|| ||
R—C—O—C—R

Answer 14

Acid anhydride

Question 15

. O
||
R—C—O—R

Answer 15

Ester

Question 16

…..O
…..||
R—C—N—R2

Answer 16

Amide

Question 17

What are intermolecular forces?

Answer 17

IMFS, the forces of attraction that may exist between the atoms and molecules of a substance (WEAK)
- hold multiple molecules together
- determine many of a substance’s properties
- the result of electrostatic phenomena
- non covalent forces

Question 18

What provides the energy required to overcome IMFs?

Answer 18

Kinetic energy

Question 19

What are intramolecular forces

Answer 19

the forces that hold atoms together in a molecule (STRONG)

Question 20

What are the three types of IMFs?

Answer 20

• Dispersion forces
• Dipole-Dipole attractions
• Hydrogen bonding

Question 21

What are van der Waals forces?

Answer 21

the three intermolecular forces collectively

Question 22

Describe dispersion forces

Answer 22

• result from the formation of temporary dipoles
• heavier molecules and atoms exhibit stronger dispersion forces than do lighter molecules and atoms
  —–> because larger atoms have greater polarizability due to the valence electrons being farther from the nucleus
• the strength of dispersion forces increases with the contact area between molecules

Question 23

What is polarizability?

Answer 23

The measure of how easy or difficult it is for another electrostatic charge to distort a molecule’s charge distribution.

Question 24

What are dipole-dipole attractions?

Answer 24

• molecules with permanent dipoles display dipole-dipole attractions
• this type of attraction is present only in polar molecules
• dipole-dipole attractions are stronger than dispersion forces
• polar molecules contain dipole dipole and dispersion forces
• adjacent molecules line up such that the partial negative pole of one molecule is as close as possible to the partial positive pole of another molecule.

Question 25

What is hydrogen bonding?

Answer 25

• only present in certain polar molecules
• unusually strong type of dipole-dipole attraction
• the strongest Van der Waals force
• need an H covalently bound to one of highly electronegative elements: Nitrogen, Oxygen, Fluorine
• strong IMFs due to highly concentrated partial charges

Question 26

IMFs in alkanes

Answer 26

• consist of nonpolar C—C bonds and very weakly polarized C—H bonds = nonpolar overall
• exhibit instantaneous dipoles due to asymmetric distributions of electrons at any point in time

Question 27

What are instantaneous dipoles?

Answer 27

• they can induce a dipole in a nearby molecule, resulting in attractive forces
• instantaneous dipole-induced dipole force is called van der waals interaction/london dispersion force

Question 28

How to boiling points of alkanes change?

Answer 28

• increasing molecular weight —–> increasing boiling point
• branched alkanes have lower boiling points than linear alkanes due to smaller surface area

Question 29

Melting points of alkanes

Answer 29

• solid alkanes are typically soft and waxy with relatively low melting points
• melting points of alkanes increase with molecular weight
• branched alkanes have lower melting points than linear alkanes

Question 30

Alkane aqueous solubility

Answer 30

• Alkanes are nonpolar substances with very weak van der waals interacitons
• VDW interactions of alkanes with water cannot overcome the strength of hydrogen bonds in water
• therefore, alkanes are not generally soluble in water

Question 31

What is the hydrophobic effect?

Answer 31

Alkane molecules cluster together and exclude water molecules