Physical Flashcards
(22 cards)
Ea solution
ΔH + RT
At ambient rt is negligible
ΔS transition state
Gain or loss of vibrational/ rotational/ translational freedom
Esterification
Carboxylic + alcohol
Negative ΔS
Lactonisation
Same bonds as esterification
Intra molecular
Less negative Δ S
Shifting TS
Stabilise products or intermediate
Shift to reactants
Hydrocarbon halogenation
Free radical
Energy differences dominated by HX
F Early as bond v strong
Cl intermediate
Br late - most radical character - most regio selective
Electrophilic addition of dienes
2 products
More substituted Alkene is thermo product
Most substituted carbocation is kinetic
Chlorobenzene + nanh2
Forms benzyne
Tagged cl carbon
Ammonia added in 2 positions
Primary kinetic isotope effect
Isotope bond made/broken in RDS
Kh > kD
Max effect where H and D TS are of equal energy
Otherwise ΔHh= ΔHd
Non-polar Aprotic
Van set waals only
Non polar protic
Specific h bonding
Dipolar protic
Solvates anions and cations
Dipolar a protic
Large dipole +be sterically hindered
Naked anions
Catalysed rate
K[recact] + Kcat[react] [cat]^n
General acid catalysis
Rate proportional to [HA]
Overall = k react + k react H+ k react HA
Occurs in buffers
Specific graphs
Log(k) against pH
Acid -1
Base +1
Linear against HA
General catalysis graphs
Log(k) against ha
Acid increases towards low pH
Ester hydrolysis
(C=O) - O cleavage acyl oxy. AC
Or
O-R cleavage alkyl oxy AL
Aac2
Protonate =O
Water nucleophile
Proton transfer
Diol carbocation
Bac2
OH nucleophile
Collapse losing phenoxide
Deprotonates carboxylic
Aac1
H addition to less nucelopilic O
AC cleavage
Water addition to carbocation
Aal1
=O protonated
AL cleavage - R must be stabilised
Carbocation + water
