Module 4 thingz Flashcards
How does a primary alcohol undergo oxidation?
1 alcohol –> aldehyde –> carboxylic acid
How does a secondary alcohol undergo oxidation?
2 alcohol –> ketone
Which are more reactive, esters or ethers?
Esters
What are imides?
C=N-R
What are amides?
O=C-H2 (primary)
What are amines?
NH2 (primary)
What is a thiol?
R-SH
How do you make a disulphide?
Two thiol’s react together in a oxidation reaction to form a disulfide
What is biological recognition?
Biological target + ligand –> Complex
What happens in addition of aldehydes and ketones for strong Nu?
- Nucleophile attacks in the first step (rate determining)
2. Electrophile attacks in the second step
What happens in addition of aldehydes and ketones for weak Nu?
Nu is often Nu-H
- Have to increase reactivity by increasing +ve charge on C
- Usually acid catalysed
1. Electrophile attacks in first step
2. Nucleophile attacks in the second step (rate determining)
Differences between Aldehydes and Ketones?
Aldehydes are more reactive then ketones because it is less strerically hindered (only one small H) and the more alkyl electron donating groups on the ketone make the central carbon less positive
What is formed when alcohol reacts with aldehyde or ketone?
A hemiacetal. It can further react with another alcohol to produce a acetal
–> goes by weak nucleophile (ROH), so H+ catalysed
What is the addition of amino compounds to aldehydes or ketones?
Amines are strong nucleophiles then alcohols
–> Further reaction to form an imine in a E1 like elimination
What are furanoses and pyranoses?
Furanoses –> four C’s and one O in the ring
Pyranoses –> Five C’s and one O in the ring
How do you distinguish between Beta and Alpha?
Alpha is down –> group on anomeric carbon is on different sides to C-5
Beta is up –> group on anomeric carbon is on same sides to C-5
What is mutarotation?
Measuring the rotation of plane polarised light by a solution of glucose shows that the equilibrium mixture is not 1:1, as the final rotation value is not the average
What is a reducing sugar?
In monosaccharides with a hemiacetal functional group at the anomeric carbon, the
chair form is in equilibrium with the open chain form, which contains a aldehyde functional group, in which they can act as reducing sugars e.g. Ag+
What are non-reducing sugars?
When hemiacetal forms are converted to acetal forms (glycosides) get a mixture of the alpha and beta forms. There is no longer an equilibrium with the open chain form (in the
absence of acid) – so acetal forms are non-reducing sugars.
What are glycosidic bonds?
Monosaccs are joint together by glycosidic bonds - hemiacetal group on one or both sugars is converted to acetal group
- -> The name of the bond reflects the carbons each mono involved in the bond
- -> unless the bond is a 1,1 linkage, the resulting disacc will still have one hemiacetal group and so it will still be a reducing sugar
What is reactivity of acid derivatives determined by?
Nucleophile reacts by forming bond to the carbonyl carbon in the rate determining step
– reactivity of acid derivative is determined by the size of the partial positive charge on the carbonyl carbon, which results from the electron withdrawing ability of the carbonyl O PLUS the L group.
What are the reactivities of acid derivatives in order from lowest to highest?
amide < carboxylic acid = ester «_space;acid anhydride = acid chloride
Why are amides the least reactive?
Due to their resonance structures. They lone pair of electrons and develop partical double bonds that keep it very stable.
What do amino acids contain?
Two functional groups - COOH and NH2 and one of 20 side chains
–> All amino acids are chiral, as have enantiomers (exept glycine)
What are fisher projections of amino acid groups like?
Have the COOH group at the top and the R group at the bottom. The position of the NH2 group then determines if the amino acid is D or L
What is the Pka’s of amino acid functional groups?
COOH = 2.5 (most easily deprotonated)
NH2 = 9.5 (less easily deprotonated)
What does amino acids change from in a titration?
From positive, to neutral, to negative
–> There is the zwitterion present in solution at psychological pH
What is the pI?
The average of the two pKa values
–> If the amino acid has a R group which has a functional group with a pKa value, then the pI is the average of the two most similar pKa values
What is electrophoresis?
A method for separating amino acids based on their charge
- -> Zwitterions will not move due to their neutral charge.
- -> Others will move towards their opposite charge
What is a peptide bond?
Amino acids are bonded together via nucleophilic substitution reactions of the amine group (the nucleophile) on one with the carboxylic acid group (the acid derivative). The bond formed is an amide.
What are terminals?
The NH2 side is the N terminal, the COOH side is the C terminal
Why is the peptide bond unreactive?
Due to resonance structures of the peptide (amide), it is unreactive towards nucleophiles and is planar and rigid
What is a protein and what is a amino acid?
<75 amino acids = peptide
>75 amino acids = protein
What is primary structure?
Sequence of amino acids
What is secondary structure?
Segments of structure along the peptide chain
e.g. alpha helix, turns etc
What is tertitary structure?
How secondary structures fit together
What is quaternary structure?
How proteins or independant peptide chains come together
What is the bonding of secondary-quaternary structures like?
Secondary-quaternary structures driven by hydrogen bonding, disulphide bond
formation between the side chains of cysteine amino acids, and the general desire
to have non-polar amino acids inside and away from the aqueous environment.
How do you make a specific peptide?
Must use protecting groups to temporarily stop groups being able to react.
- -> “Protect” an amine group with BOC group (remove later with acid)
- -> “Protect” a carb group with an OMe group (remove later with base)
- -> Catalyse reaction with DCC (can’t add acid or this will remove BOC protecting group)
- -> Remove protecting groups
Why is peptide hydrolysis difficult?
It is an unreactive acid derivative and water is a poor nucleophile
