Stereochemistry

Question 1

amino acids are naturally what stereochemistry?

Answer 1

L amino acids

S configuration

Question 2

what amino acid has an R configuration?

Answer 2

cysteine

Question 3

what does an L configuration look like?

Answer 3

Fischer projection: H is on the right hand side; OH on left hand side
normally: H will be on a dash

Question 4

what does a D configuration look like?

Answer 4

Fischer projection: H is on the left hand side; OH on right hand side
normally: H will be on a wedge

Question 5

what feature allows for proton absorption?

Answer 5

a highly conjugated system allows for pi bonds to move and creates resonance stability by delocalizing electrons

electron delocalization allows the molecule to absorb a photon in UV or visible region, having the electron jump to a higher energy state

Question 6

pyranose

Answer 6

six-membered rings

pyramids have 6 points

Question 7

furanose

Answer 7

five-membered rings

fast and furious five

Question 8

aldose

Answer 8

sugar that contains an aldehyde functional group with the carbonyl at carbon 1

Question 9

ketose

Answer 9

contains a ketone, typically at carbon 2

Question 10

hydroxy ketones

Answer 10

has an alcohol on the beta site to the carbonyl

can undergo tautomerization via an enediol intermediate to produce aldehyde under Tollens test basic conditions

Question 11

reducing sugars

Answer 11

any sugar containing a hemiacetal is a reducing sugar

that means the sugar can acts as a reducing agent

Question 12

nonreducing sugar

Answer 12

is an acetal or ketal

does not have H on an oxygen that can be removed to reduce something

just has two OR groups

Question 13

mutarotation

Answer 13

conversion between alpha and beta anomers via an open chain intermediate

hemiacetal opens into linear form and then cyclizes back to hemiacetal in opposite configuration

Question 14

can ketones give a positive Tollens test?

Answer 14

Tollens test is looking for aldehydes and hydroxy ketones and are oxidized to carboxylic acids by Ag(NH3)2+

ketoses can undergo tautomerization to become an aldehyde and be in aldose form

Question 15

terpenes

Answer 15

lipid precursor to steroids and lipid signaling molecules

compounds are made up of branched five-carbon groups, called isoprene units

Question 16

isoprene units

Answer 16

branched five carbon group that makes up terpenes
branched end refers to head
unbranched end refers to tail

Question 17

monoterpene

Answer 17

has 2 isoprene units

Question 18

triterpene

Answer 18

has 3 monoterpenes so 6 isoterpenes

Question 19

diterpene

Answer 19

has 2 monoterpenes so 4 isoterpenes

Question 20

tetraterpene

Answer 20

has 4 monoterpenes so 8 isoterpenes

Question 21

sesquiterpene

Answer 21

1.5 monoterpenes and 3 isoterpenes

Question 22

ortho

Answer 22

when the R groups are right next to one another on an aromatic ring

Question 23

meta

Answer 23

when the R groups have one space between them on an aromatic ring

Question 24

para

Answer 24

when the R groups are directly across from one another

Question 25

In what form is carbocations most stable?

Answer 25

carbocations (+) are most stable in a tertiary structure

act as electrophiles - want to accept electrons to become neutral

Question 26

In what form is carbanions most stable?

Answer 26

carbanions (-) are most stable in a primary structure because they act as nucleophiles and want to be able to attack a carbocation without much steric hinderance

Question 27

What effect do nearby alkyl groups have on stability of carbocations and carbanions?

Answer 27

nearby alkyl groups act as electron donating so can stabilize carbocations (giving them electrons to balance out the positive charge) but will decrease stability of carbanions (making them more negative and unstable)

Question 28

The stereochemical designators α and β distinguish between?

Answer 28

epimers at anomeric carbon

Question 29

epimer

Answer 29

differ at only one stereocenter and are what create the alpha and beta difference