1a

Question 1

why are carbohydrates useful in life

Answer 1

• act as energy stores and fuels
• they form the framwork of dna and rna
• they make up the structural element of cell walls (cellulose)
• they modify proteins and lipids (glycans) for mediating cell signalling

Question 2

why are carbs good at modifying proteins and lipids for cell signalling

Answer 2

bc they have a bunch of stereogenic centres.

Question 3

formula for monosaccharides

Answer 3

Cn (H2O)n

Question 4

what is an aldose

Answer 4

a carbohydrate that has a aldehyde as one of the chain ends ,, aka it has a terminal aldehyde group present

Question 5

whats a ketose

Answer 5

ketose is a carbohydrate that has a ketone // carbonyl group in it

Question 6

okay so in carbs u have the aldose or ketone,, what else are the other C’s bonded to

Answer 6

either OH or H’s!!!

Question 7

ending when a carb has 3 C’s

Answer 7

triose

Question 8

ending when a carb has 4C’s

Answer 8

tetrose

Question 9

ending when a carb has 5C’s

Answer 9

pentose

Question 10

ending when a carb has 6 C’s

Answer 10

hexose

Question 11

what about the prefix,, what do u put if theres an aldehyde group

Answer 11

Aldo

Question 12

what about the prefic,, what do we put when theres a ketone

Answer 12

keto

Question 13

sterochem,, what do we mean

Answer 13

if something is R or S config,, we make sure u put the lowest priority group as the 4,, also make sure this is dashed away from us or we have to flip the config we get

Question 14

number of stereoisomers can be found with which formula

Answer 14

steroisomers = 2^n

where n is the number of stereogenic centres

Question 15

when we label a fisher projection,, where do we start numbering the stuff from

Answer 15

for an aldose,, aka a carb with a terminal aldehyde,, we start labelling from the aldehyde,, we say this is one!!!

Question 16

do enantiomers behave the same in chiral environments

Answer 16

nope!!!

enantiomers are non superimposable mirror images of eachother meaning one will have an S config and one will have an R config. they will behave and react differently in chiral env

they will behave and react the same in non chiral environments tho!!!

Question 17

R can also be called

Answer 17

D
Dextro
(+)

Question 18

which way does D // dextro rotate plane polarised light

Answer 18

dextro rotates plane polarised light clockwise

Question 19

what can the S one be called

Answer 19

L
Levo

Question 20

which direction does L//levo rotate plane polarised light

Answer 20

rotates plane polarised light anticlockwise!!

Question 21

what can make a molecule change the way it rotates plane polarised light

Answer 21

changing the solvent and concentration can make the molecule rotate plane polarised light in the oppsosite direction!!!

Question 22

when are two things considered enantiomers in terms of their sterogenic centres

Answer 22

if all their stereogenic centres are opposites,, they are said to be enantiomers

aka if one has S and the other one has R,, they are said to be enantiomers

Question 23

what is a diasteroisomer

Answer 23

when not all of their chiral centres are opposite.

aka when one has SR and the other one has SS

SSS and SRR
these would also be diastereoisomers

Question 24

what are epimers

Answer 24

they are basically what we though diatereoisomers were this whole time.

its when things are diastereoisomers but only one of their chiral centres are opposite.

SS and SR

Question 25

when we have a fischer conformation,, how do we assign D and L config

Answer 25

we assign it based on the highest numbered secondary alcohol. aka the one furthest from the terminal aldehyde that would be given the number 1. if its pointing right = D if its pointing left = L

Question 26

aldoses all have what config

Answer 26

they all have the D config!! aka all have the highest numbered terminal alcohol pointing to the right!! we dont care about any other alcohol

Question 27

okay so how do we assign D or L config to aldose // ketose

Answer 27

we find the aldehyde // ketone and we number this as 1,, we then keep numbering downwards. we then find the secondary alcohol with the highest number we see if this is pointing left or right. right = D left = L

Question 28

ketoses all have what config

Answer 28

they all have the D config. aka the secondary OH with the largest number is pointing right!!

Question 29

aldehyde and base gives

Answer 29

base catalysed hemiacetal synthesis!!

Question 30

describe base catalysed hemiacetal synthesis

Answer 30

base attacks C=O C,, and moves double bond to the O. O is protonated so u get R H BASE OH

Question 31

ketone with base gives what

Answer 31

base catalysed hemiketal

Question 32

descrbe a base catalysed hemiketal

Answer 32

u attack the C=O C with a base and move the double bond to the O,, the O turns into H2O and the bases lone pair kicks off the H20,, another BASE then attacks the C=O and u get R R BASE OH

Question 33

whats an acetal

Answer 33

when u have R H BASE BASE

Question 34

whats a ketal

Answer 34

when u have R R BASE BASE

Question 35

acid catalysed hemiacetal synthesis

Answer 35

u have an aldehyde and bc its acidic conditions u protonate the carbonyl O. then the nase attacks it and u get a R H BASE OH

Question 36

when can OH be kicked off

Answer 36

when u use an E1CB mechanism aka when u kick it off using an enolate!!!

Question 37

so how can we remove OH if its a lg

Answer 37

u need to protonate it to form H20 and then kick this off bc water is a good lg

Question 38

hemiacetal and basic hydrolysis

Answer 38

base deprotonates the OH on R H BASE OH to give O-. this O- reforms the carbonyl and kicks off the base to give an aldehyde

Question 39

hemiacetal and acidic hydrolysis

Answer 39

the BASE in R H OH BASE is protonated to make the O+ and unstable. the lone pair on the OH reforms the carbonyl bond and kicks off the base!!! this leaves u with an aldehyde.

Question 40

why is intermolecular hemiacetal formation favoured over intramolwecular hemiacetal formation

Answer 40

its both kinetically and thermodynamically favoured bc ur not reducing the entropy bc u. still have 1 molecule as ur reactant and ur product.

Question 41

what is a lactol

Answer 41

an intramolecular reaction where an OH attacks a carbonyl in the same molecule to give a cyclic structure!!

Question 42

how are lactose formed and how should we number then

Answer 42

so think what we want to make a 5 or 6 membered ring, find an OH and a C=O and see if they are numbered 1-6 or 1-5 make sure u count from the O of the OH and the C of the C=O!! u basically just use the lone pair on OH to attack the C of the C=O,, which then moves e- to the O to form O-,, which is them protonated to give OH

Question 43

what is made when making lactols

Answer 43

u make a new stereogenic centre bc ur forming a bond with the carbonyl C and the O of the OH and are removing the double bond frm the C=O

Question 44

when drawing a lactol,, what model do we use

Answer 44

we use the mills model where the C-OH of the bond we just made is curlyyyyy. the C of this C-OH aka the C that used the be C=O is now a stereogenic centre!!!

Question 45

okay so when we have the fischer projection and are trying to draw out the acc molecule,, what should we think

Answer 45

we should think that the things pointing to the RHS are gonna be pointing towards us on thw actual molecule projection. and the stuff pointing to the LHS will be pointing away from us on the actual molecule projection!!!