Polarity and Solubility

Question 1

Define/draw an alkane group.

Answer 1

C(n)H(n+2)

Question 2

Differentiate between aliphatic and aromatic hydrocarbon rings.

Answer 2

Aliphatic = no conjugated double bond system
Aromatic = conjugated double bond system (among other characteristics; e.g. benzene/phenyl)

Question 3

Define/draw an alcohol group.

Answer 3

R-OH

Question 4

Define/draw an ether group.

Answer 4

R-O-R

Question 5

Define/draw an aldehyde group.

Answer 5

R-COH

Question 6

Define/draw a ketone group.

Answer 6

R-CO-R

Question 7

Define/draw a carboxylic acid group.

Answer 7

R-COOH

Question 8

Define/draw a fatty acid molecule.

Answer 8

R-COOH, usually where R = a long hydrocarbon chain (≥14 C).

Question 9

Define/draw an ester group.

Answer 9

R-COO-R

Question 10

Define/draw an amine.

Answer 10

R-NH2

Question 11

Differentiate between primary, secondary, and tertiary amines.

Answer 11

Primary - N is bound to 1 R group
Secondary - N is bound to 2 R groups
Tertiary - N is bound to 3 R groups

Question 12

Differentiate between primary, secondary, and tertiary alcohols.

Answer 12

Primary - central C to which OH group is bound is also bonded to 1 R group
Secondary - central C to which OH group is bound is also bonded to 2 R groups
Tertiary - central C to which OH group is bound is also bonded to 3 R groups

Question 13

Define/draw an amino acid.

Answer 13

H3N-COOH-R

Question 14

Define/draw an amide.

Answer 14

R-CO-NH2

Question 15

Differentiate between a primary, secondary, and tertiary amide.

Answer 15

Primary - N is bound to only 1 R group (the R-CO group)
Secondary - N is bound to 2 R groups (including the R-CO group)
Tertiary - N is bound to 3 R groups (including the R-CO group)

Question 16

What is a polyamide? Give a biologically-relevant example.

Answer 16

Long chain of amides formed by condensation of the amide’s H and a carboxylic acid’s OH; e.g. polypeptides (proteins).

Question 17

What differentiates chlorophyll a from chlorophyll b?

Answer 17

Chlorophyll a contains a methyl group at the position where chlorophyll b has an aldehyde group.

Question 18

Describe the 2 main types of intermolecular bonds.

Answer 18

Ionic - electrons are transferred from one element to another to form a cation and anion which balance one another’s charges
Covalent - electrons are shared by elements to give rise to a stable valence shell in both

Question 19

What chemical characteristic determines whether a bond is ionic or covalent?

Answer 19

Electronegativity of each element in the bond and the difference in EN.

Question 20

Define electronegativity.

Answer 20

An element’s relative affinity for electrons.

Question 21

What is polarity?

Answer 21

Asymmetrical distribution of charge within a molecule due to differences in the electronegativity of its component atoms/elements.

Question 22

Describe the 3 types of polarity that can exist within a bond.

Answer 22

1. Nonpolar - no difference in electronegativity between member atoms
2. Slightly polar - some difference in EN between member atoms which results in electrons being “held” slightly closer to one atom
3. Strongly polar - extreme difference in EN between member atoms which restuls in electrons being transferred completely to the more EN atom (ionic bond)

Question 23

Define a dipole moment.

Answer 23

Vector describing the direction and magnitude of charge production across a bond or the vector sum of polar bonds within a molecule, which determines areas of positive and negative charge within the molecule.

Question 24

Define inductive effects.

Answer 24

Removal or addition of electron density by a strongly or weakly EN atom or functional group across sigma (single) bonds.

Question 25

Describe the 3 main types of intermolecular bonds.

Answer 25

1. Ion-dipole bonds - attraction between ions and areas of opposing charge within covalent molecules
2. Hydrogen bonds (dipole-dipole) - interaction between H atoms bound to a highly EN central atom and lone electron pairs on the highly EN central atom of another molecule (i.e. O or N)
3. van der Waals forces - interaction between temporary dipoles created by distortion of electron clouds as nonpolar molecules near one another

Question 26

How does distance between functional groups affect induction within a molecule?

Answer 26

Inductive effects exerted by a functional group diminish the further that functional group is from the area of electron density (i.e. functional group) being affected.