Module 4 Flashcards
Alcohols
Undergo nucleophilic substitution
Can be oxidised
Form esters with carboxylic acids
Primary oxidised to aldehydes then carboxylic acid
Secondary oxidised to ketone
Tertiary not readily oxidised
Ethers and esters
Ethers may be cleaved but are generally unreactive
Esters are more easily cleaved by reaction with nucleophiles
Amides
Not basic or nucleophilic
Acid derivates, can react with nucleophiles such as water but not very reaction
Addition reaction of aldehyde and ketone with strong nucleophile
Nucleophile attacks in first step (rate determining)
Electrophile attacks in second step (fast)
Aldehydes vs Ketones
Aldehydes are more reactive than ketones
C of ketone is less attractive to nucleophiles
Aldehydes are less stericly hindered
Hemiacetal
R-OH
R-OR
Carbohydrates
Reducing sugar
Acetal
R-OR
R-OR
Complex carbohydrates
Non-reducing sugar
Addition of amino compounds
R-NH2 stronger nucleophile than ROH, as the lone pair of electrons on nitrogen are much loosely held and easily shared
Strong nucleophile
Fischer projection
Highest oxidised carbon at the top (i.e. CHO)
The longest carbon chain is the vertical bonds
Bonds up and down are into the page - -
Bonds to the side are out of the page —
Fischer projection D orientation
If the non-hydrogen atom (usually OH or NH2) is pointing to the right = D
Fischer projection L orientation
If the non-hydrogen atom (usually OH or NH2) is pointing to the left = L
Aldoses - size
Varying number of carbons
As no. of carbons increase, no. of chiral carbons and no. of stereoisomers increases
2^n (e.g. 2^4 = 16)
Cyclic hemiacetal
Molecule contains C=O and OH
Anomeric carbon
C atom bonded to two O atoms
Furanose
4 x C
1 x O
5 member ring
Pyranose
5 x C
1 x O
6 member ring
Glucose
One of the most abundant monosaccharides
Found in alpha-D-glucopyranose and beta-D-glucopyranose
B-D-glucopyranose
The D has a CH2OH group pointing up at C5 and an OH group pointing down at C1 (anomeric carbon)
Beta = same side
a-D-glucopyranose
CH2OH pointing up at C1 (anomeric carbon), OH pointing down
One side up one side down = alpha
Sucrose
D-glucose is in pyronose form
D-fructose is in furanose form
Most reactive to least reactive
Acid chloride —> acid anhydride —> ester —> carboxylic acid —> tertiary amide —> secondary amide —> primary amide
Why are amides least reactive?
C-N bond has partial double bond character (shorter than single bond, harder to break)
How to calculate pI
Half way between pKa molecules closest in value
Find average (add together, divide by 2)
Nucleosides
Combination of a sugar unit with a purine or pyrimidine base
Base attached to sugar at C-1 in the B-orientation
