CHEM10006 Study Guide - Final Guide: Amino Acid, Glycosidic Bond, Tautomer
12 Jun 2018
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to O in ring, and an OH group attached, have hemiacetals
Non-reducing sugars: Glycosides, do not mutarotate: A sugar
is bound to another functional group via a glycosidic bond;
have acetals
Tautomerism: Type of isomerism in which the only structural
changes that take place involve the positions of protons
Keto-enol tautomerism: A chemical equilibrium between a
keto form (ketone or aldehyde) and an enol (an alcohol), which
are tautomers of each other
Tautomer: Constitutional isomers of organic compounds that
readily interconvert
Keto form of each base normally present in DNA critical for
correctly matching base pairs
Imino & enol forms are rare;
mispairing results from the
change of one tautomer into
another: tautomeric shift
Disaccharides & polysaccharides
Maltose: Joining of
anomeric centre of
one D-glucose and
the 4-position of
another, reducing
Sucrose: Joining
anomeric centres of
D-glucose &
D-fructose,
non-reducing
Lactose: D-galactose & D-glucose
linked by a 1,4 beta glycosidic
linkage, a reducing sugar
their own electrons away from the bonding bair
Carboxyl functional group
Strongly polarized
Nucleophiles can be added, but X acts as a leaving group:
Nucleophilic substitution: addition & elimination
Reactions of carboxyl functional group
Reduction: e.g. by LiAlH
4
, forms an aldehyde that is rapidly
reduced to an alcohol
Acid chlorides: Prepared from carboxylic acids & thionyl
chloride
Esters: Acid chlorides react readily with alcohols to yield
esters
Amides: Prepared from primary or secondary amines
Anhydrides: Similar reactivity to acid chlorides
Haworth projections
D/L Configuration
L configuration has a hydroxyl group on the anomeric carbon
on the left in a Fischer projection, and R configurations have
the hydroxyl group on the right
Proteins
Amino acids: Basic amino group + acidic carboxyl group, 20
naturally occurring
R group: Side chain specific to the amino acid
Cysteine: Naturally occurring alpha amino acid
Chirality: Glycine is achiral, for all other amino acids, alpha
carbons are centres of chirality; stereochemical reference for
amino acids is L-serine
Amide bond: Formed by the -NH
2
of one amino acid and -CO
2
H
of the next
Peptide: Smaller chains with fewer than 50 units
N-terminus: Left
C-terminus: Right
Determining peptide sequence:
1. Identify N-T
2. Partial acid hydrolysis
3. Identify then align peptides
Peptide bond: Bond between amino acids, the carboxyl group
Document Summary
To o in ring, and an oh group attached, have hemiacetals. Non-reducing sugars: glycosides, do not mutarotate: a sugar is bound to another functional group via a glycosidic bond; have acetals. Tautomerism: type of isomerism in which the only structural changes that take place involve the positions of protons. Keto-enol tautomerism: a chemical equilibrium between a keto form (ketone or aldehyde) and an enol (an alcohol), which are tautomers of each other their own electrons away from the bonding bair. Nucleophiles can be added, but x acts as a leaving group: Reduction: e. g. by lialh , forms an aldehyde that is rapidly reduced to an alcohol. Acid chlorides: prepared from carboxylic acids & thionyl chloride. Esters: acid chlorides react readily with alcohols to yield esters. Tautomer: constitutional isomers of organic compounds that readily interconvert. Keto form of each base normally present in dna critical for correctly matching base pairs.
