Organic Chemistry Chapter 10: Nitrogen and Phosphorus-Containing Compounds

Question 1

The a-carbon of an amino acid is attached to

Answer 1

an amino group
a carboxyl group
a hydrogen atom
a R group

Question 2

All amino acids are chiral, except

Answer 2

glycine

Question 3

All amino acids in eukaryotes are L or D?

Answer 3

L

Question 4

What is the only amino acid that does not have S stereochemistry?

Answer 4

cysteine - R

Question 5

Amphoteric

Answer 5

they can act as acids or bases – amino acids

Question 6

Zwitterions

Answer 6

dipolar ions

Question 7

Nonpolar nonaromatic amino acids

Answer 7

alanine, valine, leucine, isoleucine, isoleucine, glycine, proline and methionine _ tend to be hydrophobic

Question 8

Aromatic amino acids

Answer 8

tryptophan, phenylalanine, tyrosine _ tend to be hydrophobic

Question 9

Polar amino acids

Answer 9

serine, threonine, asparagine, glutamine and cysteine _ tend to be hydrophilic

Question 10

Negatively charged amino acids

Answer 10

contain carboxylic acids in their R groups and include aspartic acid and glutamic acid _ tend to be hydrophilic

Question 11

Positively charged amino acids

Answer 11

contain amines in the R groups and include arginine, lysine and histidine _ tend to be hydrophilic

Question 12

Peptide bonds form by _ and can be cleaved by __

Answer 12

Formed by condensation – cleaved by hydrolytically

Question 13

What is needed to cleave a peptide bond?

Answer 13

strong acid or base

Question 14

What restricts motion about the C-N bond in a peptide bond?

Answer 14

resonance of the peptide bond

Question 15

Polypeptides

Answer 15

Strings of amino acids

Question 16

What are two ways to synthesize amino acids in the lab?

Answer 16

Stecker synthesis - from an aldehyde

Gabriel synthesis - from potassium phthalimide, diethyl bromomalonate and an alkyl halide

Question 17

Strecker synthesis

Answer 17

1. Aldehyde is mixed with ammonium chloride and potassium cyanide. The ammonia attacks the carbonyl carbon, generating and imine.
2. Imine is then attacked by the cyanide, generating an aminonitrile.
3. Aminonitrile is hydrolyzed by two equivalents of water, generating an amino acid.

Question 18

Gabriel Synthesis

Answer 18

1. Phthalimide attacks the diethyl bromomalonate, generating a phthalimalonic ester
2. The phthalimidolmalonic ester attacks an alkyl halide, adding an alkyl group to the ester
3. The product is hydrolyzed, creating phthalic acid (with two carboxyl groups) and converting the esters into carboxylic acids.
4. One carbozylic acid of the resulting 1,3-dicarbonyl is removed by decarboxylation

Question 19

Phosphorus is found in

Answer 19

Inorganix phosphate, a buffered mixture of hydrogen phosphate and dihydrogen phosphate

Question 20

What is the bond in the backbone of DNA? What is released when it forms

Answer 20

Phosphodiester bonds - pyrophosphate is released

Question 21

Why are phosphate bonds high energy?

Answer 21

large negative charges in adjacent phosphate groups and resonance stabilization of phosphates.

Question 22

Organic phosphates

Answer 22

are carbon-containing compounds that also have phosphate groups. The most noteable examples are ATP and DNA

Question 23

Why can phosphoric acid act as a buffer over a large range of pH values?

Answer 23

it has three hydrogens, each with a different pKa