Organic 1 Flashcards
Conjugated System
a system of coplanar, overlapping (adjacent) π orbitals
Brønsted definition
Acid: proton donor
Base: proton acceptor
Lewis definition
Acid: lone pair acceptor
Base: lone pair donor
R-stereochemistry
clockwise movement of priority groups
S-stereochemistry
anti-clockwise movement of priority groups
Chiral centre
geometric property of a rigid molecule of being non-superimposable on its mirror image
Pro-chiral
when a molecule can have its mirror plane broken to create a chiral centre in a single step
Constitutional isomers
same atoms, but different connectivities
Configurational isomers
molecules have identical constitution but they have different configurations (spatial arrangements)
Enantiomers
- have opposite absolute configurations
- same chemical properties towards achiral reagents
- same physical properties in achiral environments
- rotate plane of polaries light in opposite directions to the same extent
- react differently to other chiral species
- can be separated by resolution
Diastereoisomers
- May be chiral or achiral
- Differ at one or more but not all chiral centres
- they have different chemical and physical properties
Conformational isomers
they have the same bond connectivity and configuration but different spatial arrangements of atoms
Factors that affect acidity and basicity
- the strength of the H-A bond
- the stability of the conjugate base
- the solvent/ solvation effects
What are requirements for efficient reactions?
- similar energies of key orbitals (high energy Nu HOMO/ low energy electrophile LUMO)
- good alignment (coplanar) of the HOMO-LUMO – efficient orbital overlap
Characteristics of hard nucleophiles and bases
- high charge density
- low energy HOMO
- X- is basic
- Like to attack H+ and C=O
e.g. RO- , NH 2 - RLi
Characteristics of soft nucleophiles and bases
- low charge density
- high energy HOMO
- X- is not basic
- Like to attack sp3 C
e.g. RS-, I-, R 3 P
Conditions for organometallic reactions
- low temperature (they’re very reactive)
- use aprotic solvents (THF) as protic solvents such as water have acidic protons
- done in a dry, inert atmosphere of nitrogen or argon (very reactive with oxygen)
Are organometallics acidic or basic?
Very basic
