Organic Chemistry DAT Notes
Organic Chemistry DAT Studying Notes
The Word Document for this Page is located here:
Organic Chemistry DAT Notes
SN1 vs. SN2
SN1: 1) reactivity: 3 o halides > 2 o > 1 o
2) rate = k[halide]
3) stereochemical result = partial inversion and racemization
4) accelerated by
polar protic solvents (ex. H 2O & CH 3OH) – stabilize the carbocation
slow step = formation of carbocation
SN2: 1) stereochemical result = 100% inversion
2) rate = k[halide][Nu]
3) backside attack of Nu on X
– (sp 3 C sp 2 sp 3)
4) best in
polar aprotic solvents (ex. DMSO, HMPT, acetone)
5) best w/
strong Nu (ex. CN –)
reactivity: methyl > 1 o > 2 o > 3 o
leaving groups: I > Br> Cl > F Subsitution usually favored over elimination
E1 vs. E2
It is a two-step process of elimination:
ionization and deprotonation.
and some secondary substituted alkyl halides. tertiary Reaction mostly occurs in complete absence of base or presence of only a weak base.
No antiperiplanar requirement.
E1 eliminations happen with highly substituted alkyl halides due to 2 main reasons.
Highly substituted alkyl halides are bulky, limiting the room for the E2 one-step mechanism; therefore, the two-step E1 mechanism is favored.
Highly substituted carbocations are more stable than methyl or primary substituted. Such stability gives time for the two-step E1 mechanism to occur.
N1 and E1 pathways are competing, the E1 pathway can be favored by increasing the heat.
It is a one-step process of elimination with a single
. transition state Typical of secondary or tertiary substituted alkyl halides. It is also observable with primary alkyl halides if a hindered base is used.
Because E2 mechanism results in formation of a Pi bond, the two leaving groups (often a hydrogen and a
) need to be halogen . Involves an coplanar antiperiplanar has transition state conformation with lower energy. staggered Reaction often present with strong
. base In order for the pi bond to be created, the
of carbons need to be lowered from hybridization sp to 3 sp . 2
Elimination > Substitution conditions
is influenced by reaction rate ‘s reactivity. There is a certain level of competition between halogen elimination reaction and . More precisely, there are competitions between E2 and nucleophilic substitution and also between E1 and S N 2 . Substitution generally predominates and elimination occurs only during precise circumstances. Generally, elimination is favored over substitution when S N 1
Tollens (+) = aldehyde or alpha-hydroxy ketone
2,4 DNP (+) = carbonyls
Wittig – makes C=O C=R
4 – cleaves diols carbonyls
o alcohols dehydrate the fastest Dipole molecule required for IR signal.
More conjugated = more UV absorption @ longest wavelength
Low T = kinetic control = 1,2 addition
Smallest heat of hydrogenation = more stable alkene (3
o) Allenes (-C=C=C-) can be chiral if there are 2 diff. substituents on each side.
Sulfonation = reversible rxn
E-donating group more activating group = 1
st atom is more e-negative
You have to login to post comment!!