CHEM20018: Reactions and Synthesis

Tautomerism

Isomerism involving proton and double bond movement.

Alpha Substitution

Reactions involving substitution at alpha carbon.

Condensation Reactions

Reactions forming larger molecules by combining smaller ones.

Keto-Enol Tautomerism

Equilibrium between ketones and their enol forms.

Enol

Tautomer with alpha proton on oxygen.

Enolate

Tautomer with negatively charged oxygen.

Acid Catalysed Mechanism

Formation of tautomers using acid as catalyst.

Base Catalysed Mechanism

Formation of tautomers using base as catalyst.

Self-Catalysed Mechanism

Two ketones combine to form tautomers.

Symmetrical Ketones

Both sides have identical alpha carbons.

Asymmetrical Ketones

Different alpha carbons on either side of carbonyl.

E/Z Isomerism

Geometric isomerism due to double bond position.

Non-Enolisable Carbonyls

Carbonyls lacking alpha hydrogens cannot enolize.

Conjugated Enols

Enols formed by enolization at gamma position.

Dicarbonyl Stabilization

1,3 disubstituted carbonyls yield more stable products.

Enol Reactivity

Enols act as nucleophiles in reactions.

Enolate Reactivity

Enolates are more reactive than enols.

Acidity of Carbonyls

Carbonyls increase acidity, lowering pKa values.

Lithium Diisopropylamide (LDA)

Strong base for forming enolates from carbonyls.

Sodium Ethoxide

Weaker base used for enolizing more acidic carbonyls.

Racemisation

Equilibrium between enol/enolate with opposite stereochemistry.

Epimers

Diastereoisomers differing by one stereocentre.

Halogens

Reactive electrophiles that can react with enols.

Monobromination

High yield reaction producing brominated compounds.

Debromination

Lower yield reaction removing bromine from compounds.

Alpha Haloketones

Halides act as leaving groups in Sn2 and E2.

Dibromination

Produces vinyl halides through double bromination.

Haloform Reaction

Uses excess halogen to substitute alpha hydrogen.

Hell-Volhard-Zelinsky Reaction

Alpha halogenation of carboxylic acids via enol.

Acetic Acid Reaction

Forms acid bromide via phosphorous tribromide treatment.

Aldol Reaction

Aldehyde or ketone forms nucleophilic enolate.

Beta Hydroxy Aldehyde

Product of aldol reaction before dehydration.

Aldol Condensation

Elimination of water from beta hydroxy aldehyde.

Dicarbonyl Reaction

Can produce carbocycles through self-reaction.

Non-enolisable Aldehydes

React to form mixed aldol products.

Aldehyde Reactivity

Less bulky, more reactive than ketones.

Ketone Stability

More stable carbocations, less reactive than aldehydes.

Malonate Chemistry

Synthesis of carboxylic acids via alkylation.

Acetoacetate Chemistry

Synthesis of methyl ketones via alkylation.

Deprotonation

Base-induced removal of hydrogen from compounds.

Saponification

Hydroxide treatment converting esters to carboxylates.

Michael Reaction

Conjugate addition of enolate to unsaturated carbonyl.

Mannich Reaction

Three-component reaction forming Mannich bases.

Mannich Base Applications

Synthesis of compounds like tropinone.

Mannich Reaction

Synthesis method for fluoxetine (Prozac).

Betti Reaction

Used in drug synthesis processes.

Carbohydrates

Hydroxy ketones or aldehydes, suffix '-ose'.

Fischer Projections

Representation showing stereochemistry of sugars.

D-glyceraldehyde

Most oxidized carbon at the top in projections.

L-Descriptor

Highest numbered stereochemical centre on the left.

D-Descriptor

Highest numbered secondary alcohol on the right.

Lobry de Bruyn-Alderda van Ekenstein Reaction

Interconversion between aldose and ketose via enediol.

Aldose

Sugar with aldehyde group at chain's end.

Ketose

Sugar with ketone group within the chain.

Simple Carbohydrate Reactions

Carbonyls reduce to alcohols; aldoses oxidize to acids.

Killani-Fischer Ascent

Cyanide addition to aldehyde forms cyanohydrin.

Cyanohydrin

Intermediate formed from aldehyde and cyanide.

Reducing Sugar

Glucose identified as a reducing sugar.

Hemiacetals

Formed from aldoses condensing, creating anomeric centre.

Anomeric Centre

New stereochemical centre from hemiacetal formation.

Furanose

5-membered ring sugar structure.

Pyranose

6-membered ring sugar structure.

Mutarotation

Optical rotation change from anomer interconversion.

Glycosides

Non-reducing sugars formed from hemiacetals.

Disaccharides

Two monosaccharide units linked by glycosidic bond.

Polysaccharides

Long chains of monosaccharides, e.g., glycogen.

Second Law of Thermodynamics

Entropy change equals system plus surroundings entropy.

Spontaneous Reactions

Characterized by negative delta G value.

Lattice Enthalpy

Energy change when ionic solids form from gaseous ions.

Hess's Law

Total enthalpy change equals sum of individual steps.

Born-Haber Cycle

Calculates lattice enthalpies experimentally.

Born Forces

Lower lattice energy by 10%, includes repulsions.

Born-Lande Equation

Calculates lattice energy using ion charge and distance.

Born-Mayer equation

Describes lattice energy in ionic compounds.

Kapustinskii equation

Estimates lattice energy for unknown structures.

Lattice enthalpy

Energy change when ionic solid forms from ions.

Hydration enthalpy

Energy change when ions interact with water.

Solubility of ionic solids

Affected by lattice and hydration enthalpy.

Endothermic process

Absorbs heat, like KI dissolution.

Basic oxide

Reacts with acids, transfers protons.

Amphoteric oxide

Acts as acid or base in reactions.

Ellingham diagram

Shows temperature stability of metal oxides.

Delta G

Free energy change; negative indicates spontaneity.

Standard potential

Indicates stability of an ion in environment.

Latimer diagram

Represents complex redox reactions of molecules.

Oxidation number

Charge of an atom in a compound.

Frost diagram

Relates Gibbs free energy to oxidation states.

Disproportionation

Reaction where a species is both oxidized and reduced.

Entropy increase

More gas moles lead to higher entropy.

Proton transfer

Key feature of basic oxide dissolution.

Group 1 metals

Highly reactive with oxygen, form oxides.

Potassium superoxide

Absorbs CO2, releases O2 for purification.

Dissolution factors

Include solute breakup, intermolecular force disruption.

Hydration energy

Higher with mismatched ion sizes.

Thermodynamic graphs

Visualize relationships in chemical thermodynamics.

Disproportionation

Species above line undergoes in Frost, E on right more positive than E left in Latimer

Elemental Form

Oxidation number 0 at origin.

Standard Potential

Potential change multiplied by oxidation number change.

Stability Field of Water

pH and potential range for water stability.

Nernst Equation

Calculates potentials under non-standard conditions.