Organic Flashcards
(34 cards)
What is the naming scheme for benzene (I.e if it is a side group)
If benzene is part of something it is a phenyl group, if the benzene has anything attached too it the group becomes something arene e.g. fluoroarene
What is a meso compound
A compound that has stereogenic centers but is not chiral (NEVER say chiral center)
What happens if you swap a bond at a stereogenic centre
It’s absolute configuration changes from R too S or vice versa
What is a modal plane and where could you find one
An area of an atom where electrons cannot exist
They are located between the 2 nodes of a p orbital
What are the two ways p orbitals can combine and what is the difference between them
End-on
Edge-on
End on forms a symmetrical line like a sigma bond whereas edge on forms a shape that resembles the Pi symbol hence the name Pi bond
What is the relationship between atomic orbitals and molecular orbitals
They are always equal
If there are two atomic orbitals how many molecular orbitals will there be and what type of bonding will they be
2 atomic orbitals ALWAYS gives 2 molecular orbitals one of which will be bonding the other anti bonding
Is bonding or anti-bonding higher in energy
Anti-bonding is much higher in energy
What are the 3 main rules when forming molecular orbitals
- The two atoms must be similar in energy (not like a H and a Cl)
- They should be about the same size (not a 2s and a 3s)
- They must have appropriate symmetry (pi bonds cannot be formed between an s and a p orbital)
What does a resonance arrow look like
A single double headed arrow that shows the conversion between 2 resonance forms
What is conjugation
When a series of alternating double and single bonds spreads electron density between the two
What is the minimum number of atoms that can share a delocalised electron
3
For the purposes of conjugation what else can count as a double bond
One or more line pairs of electrons
What are HOMO and LUMO
HUMO = highest occupied molecular orbital (highest energy at rest)
LUMO = lowest unoccupied molecular orbital (not present at rest but first to become present when energy is applied)
What happens during the hybridisation of orbitals (2s and 2p) for sp3, sp2 and sp hybridisation
- They create 4 sp3 orbitals which have 3/4 of the energy of a p orbital (tetrahedral)
- They create 3 sp2 orbitals which have 2/3 of the energy of a p orbital and must form a double bond (trigonal planar)
- They create 2 sp orbitals which have 1/2 of the energy of a p orbital and must contain a triple bond (linear)
What are constitutional isomers
They have the same atoms but are connected differently
What are conformational isomers
Isomers that differ because of a C-C bond rotation
What are CIP rules for determining isomerism
- Work out which is the lowest priority group and place that at the back of the atom
- Label the remaining atoms in priority order from 1-3
- Draw a continuous arrow from 1 too 3 if that is clockwise you have an R enantomer otherwise it is an S enantomer
Which is the most stable position axial or equitorial
Equatorial is always the more stable position as this does not form any 1,3-diaxial-interactions so the the larger atom is usually placed in the equitorial position
What atom is used as the baseline for inductive effect
Hydrogen
What is the difference between an E1 and an E2 reaction
Both are eliminations however E1 only forms 1 carbocation whereas E2 forms 2
What is the usual ration of Sn1 too E1 products
2:1
What type of isomer is usually the major product of an elimination reaction and why
The E-isomer as the bulkier groups are further from each other making this more sterically stable
What do E2 reactions require
A leaving group and a proton at 180 degrees of each other
