Organic Chemistry Chapter 10: Nitrogen and Phosphorus-Containing Compounds Flashcards
(23 cards)
The a-carbon of an amino acid is attached to
an amino group
a carboxyl group
a hydrogen atom
a R group
All amino acids are chiral, except
glycine
All amino acids in eukaryotes are L or D?
L
What is the only amino acid that does not have S stereochemistry?
cysteine - R
Amphoteric
they can act as acids or bases – amino acids
Zwitterions
dipolar ions
Nonpolar nonaromatic amino acids
alanine, valine, leucine, isoleucine, isoleucine, glycine, proline and methionine _ tend to be hydrophobic
Aromatic amino acids
tryptophan, phenylalanine, tyrosine _ tend to be hydrophobic
Polar amino acids
serine, threonine, asparagine, glutamine and cysteine _ tend to be hydrophilic
Negatively charged amino acids
contain carboxylic acids in their R groups and include aspartic acid and glutamic acid _ tend to be hydrophilic
Positively charged amino acids
contain amines in the R groups and include arginine, lysine and histidine _ tend to be hydrophilic
Peptide bonds form by _ and can be cleaved by __
Formed by condensation – cleaved by hydrolytically
What is needed to cleave a peptide bond?
strong acid or base
What restricts motion about the C-N bond in a peptide bond?
resonance of the peptide bond
Polypeptides
Strings of amino acids
What are two ways to synthesize amino acids in the lab?
Stecker synthesis - from an aldehyde
Gabriel synthesis - from potassium phthalimide, diethyl bromomalonate and an alkyl halide
Strecker synthesis
- Aldehyde is mixed with ammonium chloride and potassium cyanide. The ammonia attacks the carbonyl carbon, generating and imine.
- Imine is then attacked by the cyanide, generating an aminonitrile.
- Aminonitrile is hydrolyzed by two equivalents of water, generating an amino acid.
Gabriel Synthesis
- Phthalimide attacks the diethyl bromomalonate, generating a phthalimalonic ester
- The phthalimidolmalonic ester attacks an alkyl halide, adding an alkyl group to the ester
- The product is hydrolyzed, creating phthalic acid (with two carboxyl groups) and converting the esters into carboxylic acids.
- One carbozylic acid of the resulting 1,3-dicarbonyl is removed by decarboxylation
Phosphorus is found in
Inorganix phosphate, a buffered mixture of hydrogen phosphate and dihydrogen phosphate
What is the bond in the backbone of DNA? What is released when it forms
Phosphodiester bonds - pyrophosphate is released
Why are phosphate bonds high energy?
large negative charges in adjacent phosphate groups and resonance stabilization of phosphates.
Organic phosphates
are carbon-containing compounds that also have phosphate groups. The most noteable examples are ATP and DNA
Why can phosphoric acid act as a buffer over a large range of pH values?
it has three hydrogens, each with a different pKa
