Core Organic Chemistry Principles
Stereochemistry Fundamentals
Enantiomer
An enantiomer is a type of stereoisomer that is a non-superimposable mirror image of another molecule. Enantiomers have the same molecular formula and sequence of bonded atoms but differ in their three-dimensional arrangement of atoms in space.
Meso Compound
A meso compound is a type of stereoisomer that has a superimposable mirror image, despite having chiral centers. Meso compounds are achiral molecules with chiral centers.
d/l Notation
The d/l notation refers to the direction of optical rotation:
- d-: Dextrorotatory, rotates plane-polarized light to the right.
- l-: Levorotatory, rotates plane-polarized light to the left.
D/L Notation
- D-: Configuration similar to D-glyceraldehyde.
- L-: Configuration similar to L-glyceraldehyde.
These notations are used to describe the stereochemistry of chiral molecules.
Stereospecific Reaction
A stereospecific reaction is a reaction where the stereochemistry of the reactant determines the stereochemistry of the product. The reaction pathway is specific to a particular stereoisomer.
Stereoselective Reaction
A stereoselective reaction is a reaction where the reaction conditions or reagents favor the formation of one stereoisomer over another.
Asymmetric Synthesis
Asymmetric synthesis is a process where a chiral molecule is formed from an achiral starting material, resulting in an unequal amount of enantiomers.
Partial Asymmetric Synthesis
Partial asymmetric synthesis refers to a reaction that produces a mixture of enantiomers with some degree of enantioselectivity, but not necessarily with high enantiomeric excess.
Absolute Asymmetric Synthesis
Absolute asymmetric synthesis refers to a reaction that produces a single enantiomer from an achiral starting material without the influence of any external chiral source.
Sequence Rule (Cahn-Ingold-Prelog Rules)
The sequence rule is a set of rules used to assign priority to substituents in a molecule, particularly in the context of stereochemistry.
Atropisomerism
Atropisomerism is a type of stereoisomerism that arises due to restricted rotation around a single bond, resulting in non-superimposable mirror images.
Heterocyclic Compounds
Furan
Synthesis
- Feist-Benary Synthesis: Involves the reaction of α-haloketones with β-keto esters.
- Paal-Knorr Synthesis: Involves the reaction of 1,4-diketones.
Uses
- Pharmaceuticals: Furan-containing compounds are used in medications.
- Agrochemicals: Furan-based compounds are used as insecticides and fungicides.
Purine
Synthesis
- Traube Synthesis: Involves the reaction of 4,5-diaminopyrimidines with formic acid.
Uses
- Nucleic Acids: Purine bases (adenine and guanine) are essential components of DNA and RNA.
- Pharmaceuticals: Purine-containing compounds are used in medications.
Imidazole
Synthesis
- Debus Synthesis: Involves the reaction of glyoxal with ammonia.
- Radziszewski Synthesis: Involves the reaction of α-diketones with ammonia.
Uses
- Pharmaceuticals: Imidazole-containing compounds are used in medications.
- Agrochemicals: Imidazole-based compounds are used as fungicides.
Reactivity & Aromaticity Comparison
Pyrrole, furan, and thiophene are five-membered heterocyclic compounds with varying degrees of reactivity and aromaticity.
The order of reactivity is generally: Pyrrole > Furan > Thiophene
The order of aromaticity is generally: Thiophene > Pyrrole > Furan
Quinoline Structure
Quinoline is a heterocyclic aromatic compound with a benzene ring fused to a pyridine ring.
Uses
- Quinoline compounds are used in medications, such as antimalarials.
- Quinoline compounds are used as fungicides and insecticides.
Isoquinoline
Isoquinoline is a heterocyclic aromatic compound with a benzene ring fused to a pyridine ring, isomeric to quinoline.
Uses
- Isoquinoline-containing compounds are used in medications, such as analgesics and antihypertensives.
Pyridine
Pyridine is a heterocyclic aromatic compound with a nitrogen atom. Its basicity is due to the lone pair of electrons on the nitrogen atom.
Factors Affecting Basicity
- Electronegativity
- Delocalization
Named Reactions in Organic Chemistry
Clemmensen Reduction
The Clemmensen reduction is a chemical reaction that reduces aldehydes or ketones to alkanes using zinc amalgam (Zn/Hg) in acidic conditions.
Reaction
R-C(=O)-R' → R-CH2-R'
Birch Reduction
The Birch reduction is a chemical reaction that reduces aromatic rings to cyclohexadienes using alkali metals (such as sodium or lithium) in liquid ammonia.
Reaction
C6H6 → C6H8 (cyclohexa-1,4-diene)
Fundamental Organic Structures
Ethene (Ethylene)
Ethene (ethylene) has a planar, trigonal geometry around each carbon atom, with a double bond between the two carbon atoms.
Cycloalkane Conformations
Cycloalkanes are saturated hydrocarbons with a ring structure. The conformation of cycloalkanes depends on the ring size, with common conformations including:
- Chair Conformation
- Boat Conformation