Organic Structures and Mechanisms 2 Flashcards
“Me” abbreviation meaning
-CH3 Methyl
“Et” abbreviation meaning
-CH2CH3 Ethyl
“Pr” abbreviation meaning
-CH2CH2CH3 Propyl
“iPr” abbreviation meaning
-CH(CH3)2 Iso-propyl
“Bu” abbreviation meaning
-CH2CH2CH2CH3 Butyl
“tBu” abbreviation meaning
-C(CH3)3 tert-butyl
“Ph” abbreviation meaning
Phenyl
“R” abbreviation meaning
Any alkyl group
“Ar” abbreviation meaning
Any aromatic of substituted aromatic
Define heteroatom
Anything not carbon
What is a functional group level?
The no. bonds to heteroatoms from a given C atom
What is an oxidation reaction?
gain of O2 OR loss of H2 OR loss of e-
What is a reduction reaction?
gain of H2 OR loss of O2 OR gain of e-
Define inductive effects
The way in which the electronegative atoms polarize e- density in the single bond framework of a molecule
What does a -I effect mean?
e- withdrawing
What does a +I effect mean
e- donating
is -X -I or +I?
-I
is -CX3 -I or +I?
-I
is C=O -I or +I?
-I
is C-Li -I or +I?
+I
is C-Mg -I or +I?
+I
is C-CH3 -I or +I?
+I
is C-R -I or +I?
+I
What is heterolytic bond cleavage?
Forms a cation and an anion
What is homolytic bond cleavage?
Forms a radical
How does the size of an energy barrier for a reaction affect the rate of reaction?
Smaller energy barrier = faster reaction
What determines the size of the energy barrier to a reaction?
Depends on energy of the intermediate
- stable intermediates reduce the energy barrier
Define mesomeric effects (resonance)
The movement of e- density within the double bond/lone pair system of a molecule by resonance conjunction
Which takes dominates? inductive or mesomeric effects?
Mesomeric
What are hyperconjuction effects?
When there is a carbocation, an adjacent C-H or C-C bond can partially overlap with the carbocations empty orbital, donating a small amount of e- density to the empty orbital (a lot weaker than normal resonance)
Basic rules for organic mechanisms
1) Electron flow must start from an electron rich site
2) Flow must move towards and electron poor site
3) Ensure that nothing has too many bonds
4) Balance charges
5) Repeat if possible/needed
Define nucleophile (Nu-)
Electron rich species that will react with C+ or C delta +
Define base (B:)
Electron rich species that will react with H+ or H delta +
Define electrophile (E+)`
Electron poor species (usually C+ or C delta +) that reacts with a nucleophile
Define acid (H+)
Electron poor H+ pr H delta + that will react with a base
Define chemoselectivity
When several diff. sites could react, one does so with preferance
How do you choose which site to prioritize in mechanisms for the e- rich site?
- Less electronegative is BETTER (more willing to donate electrons)
I- > Br- > Cl- > F-
R-NH2 > R-OH»_space; R-F - More resonance is WORSE
- Steric hinderance is bad for nucleophiles
(ie. a tertiary alcohol is worse than primary)
How do you prioristise sites for choosing the electron poor site?
- High -I effect is good
- High +M is bad
- Resonance dominates inductive effect
What is regioselectivity?
When multiple parts of a functional group could react but one is prefered
Examples of an e- rich site
1) Negative charge
2) Lone pair
3) Double bond
4) Single bond
Examples of e- poor site
1) carbocation/H+
2) Atom adjacent to positive charge on heteroatom
3) Onward towards a positive charge
4) Partially positive charge
5) Partially positive charge at an alternating distance
How do you prioritize an intermediate product?
You want a more stable intermediate (ie. the carbocation is bonded to more carbons)
Criteria for most acidic site
- Generates the most stable conjugate base
- Negative charges should be on the most electronegative atoms
Criteria for most basic site
- Greatest electron density
- Most able to donate e- (lone pairs/negative charges should be localized, less electronegative atoms can more easily donate e- denisty)
