135A organic - substitution, elimination and addition Flashcards
(238 cards)
Alcohols are bad leaving groups. What can they be activated with (protonation of OH)
Acids/ HCl
how many substances are involved in the RDS
2 (varying the conc of both changes the rate)
how many substances are involved in the RDS
1(one one conc changes rate)
What areas on the molecule could nucleophilic sub (OH-) occur
What areas on the molecule could nucleophilic sub (OH-) occur
What areas on the molecule could nucleophilic sub (OH-) occur
What areas on the molecule could nucleophilic sub (OH-) occur
nowhere on the molecule
what does SN1 stand for
does SN1 have a carbonation intermediate
yes
primary/ secondary/ tertiary undergos SN1
tertiary (+ stable secondary cations with conjugation)
What is a carbocation structure
planar and sp2 hybridised carbon
What makes a carbocation stable? / conjugation and hyper conjugation
Could these molecules undergo SN1
1- (slow but) has conjugation due to double bond so could form a stable primary carbocation
2- very fast; conjugation and methyl groups
What factors effect wether something can undergo SN1 or SN2
Why do SN1 reactions give racemic mixtures
because the nucleophile has equal chance of attacking from the above or below/ planar carbocation
Which carbocation is the nucleophile more likely to attack/ which product will be the major
nucleophile will attack least sterically hindered/ primary will be major product
What does SN2 stand for
Does an SN2 have a carbocation intermediate
no- has transition state
What energy determines how fast a reaction will go
activation energy (higher Ea the slower the reaction)
In substitution how does the LUMO and HOMO of the reactants interact (nucleophile and electrophile)
HOMO of nucleophile and LUMO of electrophile. For a Y- the HOMO is the lone pair
The HOMO of the nucleophile goes to what bonding orbital of the electrophile
the σ* anti bonding orbital (when electrons fill it the bond breaks)
In SN2, what angle must the nucleophile and electrophile orbitals align in order to react (transition state where they leave and join simultaneously)
180°
primary/ secondary/ tertiary undergos SN2
primary and some secondary (minimal steric hinderance so nucleophile can get to σ* c-x bond)
Of primary carbocations what will increase the rate of SN2 substitutions
Reaction is faster if the carbocation is more stable/ conjugation