O Chem 1

Question 1

Peptide bonds

Answer 1

-are the same in alpha and beta amino acids; the distance between the carbonyl carbon and nitrogen does not affect the peptide bond; a peptide bond forms between 2 different aa’s

Question 2

Antibonding molecular orbitals

Answer 2

• higher energy
• less stable
• overlapping wave functions w/ opposite signs = destructive
• SMALLER chance of finding electron in this orbital

Question 3

LiAlH4

Answer 3

COOH reduced to aldehyde, then alcohol

Question 4

Conjugated molecules

Answer 4

• have unhybridized p orbitals that are excited by UV
• large conjugated molecules absorb in the color range
• as the number of conjugated systems increases, distance between HOMO and LOMO decreases = absorb things with lesser energies = larger wavelength (than UV) = absorb blue/green = look red

Question 5

aldol condensation

Answer 5

OH- attacks alpha H of carbonyl -> enolate which attacks carbonyl C
One deprotonated aldehyde/ketone attacks another
aldol = a carbonyl w/ OH at beta carbon

OH can then be dehydrated to form conjugated system
with a STRONG BASE and HEAT = condensation rxn

Question 6

Retro-aldol

Answer 6

Aldol + OH-/H2O goes to two carbonyls

Bond is broken between alpha and beta carbons of carbonyl, forming 2 aldehydes, 2 ketones, or 1 aldehyde and one ketone