IB chemistry R3.4

1-2,3,4-5,9-10,11-12,13

What is a nucleophile

An electron-rich species that is attracted to regions of positive charge it is a reactant that forms a bond to its reaction partner (the electrophile) by donating both bonding electrons.

what happens in a nucleophilic substitution reaction

a nucleophile donates an electron pair to form a new bond, as another bond breaks producing a leaving group

how does a Nucleophilic substitution reaction look

what is heterolytic fission

the breakage of a covalent bond when both bonding electrons remain with one of the two fragments formed

what is an electrophile

an electron poor species that accepts a pair of e- from the nucleophile

what do curly arrows show

the movement of e-

what is the most important thing an electrophile hould have

a low-energy unfilled orbital

what usually doens’t leave during a nucleophilic substitution reaction

an H- ion as it is unstable

what are 3 things that happen in a nucleophilic substitution reaction

a nucleophile donates a pair of electrons to form a new bond

a bond in the electrophile breaks to produce a leaving group

the nucleophile is substituted in place of the leaving group.

where do electrons go in heterolytic fission

to the atom with higher electronegativity

why can alkenes undergo electrophilic addition reactions

the pi bond is relatively weak and reactive because it is on the outside and so there is a high e- density around the double bond

what can be used as a chemical test for an alkene

Bromine water changes from brown to colorless

which Hydrogen Halides react with alkenes in order from least to most reactive and why

HI<HCl<HBr because the bond is getting longer and a longer bond, a weaker one, so faster to break

how can water react with an alkene

it can’t alone, so it needs H+ ions in order to form enough H3O+ molecules which

when is something an electrophile

if it is taking the electrons of an atom or bond

what are the only 2 ways that a C compound with 4 bonds can undergo a nucleophilic substitution reaction

SN1 or SN2 mechanism

what is SN1 mechanism step

first the Carbon Halogen bond breaks via heterolytic fission and gives a carbocation and a halide ion. the carbocation has an empty orbital and is ready to bind to any nucleophile

SNA mechanism is ——molecular

uni

how is the rate of reaction of SN1 reaction calculated and what order is it

Rate=k x concentration of halogenoalkane

in SN1, rate is the order of — meaning

1, it depends on 1 concentration

why do we not measure the rate of reaction in SN1 of both steps

rate depends on the slower elementary step, the first one

what is a reaction mechanism

it is a reaction that occurs in multiple steps and each one is called an elementary step

what is an intermediate

a substance that is formed in one elementary step and used up in the next one

what is a transition state/ activation complex

a substance that is temporary and unstable where old bonds break and new ones form and it is represented by a dashed line

what is activation energy

it is the energy needed to make the activation complex/ transition state

what conditions to SN1 reactions require

a weak nucleophile

a protic solvent (can form HB)(the HHB act as a cage and help the nucleophile)

tertiary haloalkane because it has high steric hinderence

what does SN2 mechanis require

a strong nucleophile

an aprotic solution (doesn’t form HB)

primary haloalkane because it doesn’t have high steric hinderence

what is SN2 mechanism

it is a mechanism that involves the simultaneous attack of the nucleophile on the Carbon atom and loss of the halide ion. the step is bimolecular

SN2 mechanism

SN1 mechanism

what are the reactants and products of halogenation

alkene+X2-dihaloalkane

what are the reactants and products of hydrohalogenation

alkene+HX-haloalkane

what are the reactants and products of hydration

alkene+HOH-alcohol (Wich con. H2SO4)

what are the reactants and products of hydrogenation

alkene+H2-alkane with Pt or Ni catalyst

what is steric hinderance

bulkiness

SN1 is —--specific

non-stereo

which mechanism do secondary haloalkanes do

both SN1 and SN2

how is rate affected by the identity of the leaving group

the lower the bond enthalapy and the Electronegativity of the leaving group, the easier it is to remove I>Br>Cl

how does the energy profile of SN2 mechanism look

how does the enrgy profile of SN1 look

order the carbocations from least to most stable

1<2<3

in a symmetrical alkene, which electrophilic addition reactions would result in the same product

all of them because switching the location of the atoms will result in the same product

in an asymmetrical alkene, which electrophilic addition reactions would result in the same product

with a Hydrogen Halide, there are 2 products

with an X2, 1 product

with HOH, 2 products

if there were two products that could come out of an electrophillic addition reaction with an asymetrical compound, which would be favored

the one with the more stable carbocation, so 3>2>1

why are tertiary carbocations more stable than primary

there are 2 theories here is the one that makes sense: hyperconjugation, which is a concept in organic chemistry where electrons from a sigma bond (like C-H) are shared with an adjacent empty or partially filled orbital, which helps stabilize the molecule.

what does an SN1 mechanism form

racemic mixture, 50% D, 50%L

what is Markovinkov’s rule?

if there is HX, put the H where there is more H, rich get richer

why is benzene not a strong nucleophile despite having pi orbitals

it is reluctant to give away the six delocalized pi electrons and lose the stability that arises from extensive delocalization

how does an electrophilic substitution reaction with benzene look

what happens to the delocalized e- when you bind an electrophile in order to do ESR

the resonance is disrupted and there is a positive carge where e- don’t pass through

which step in ESR with resonance is the slower one

the first one because benzene, a stable molecule is becoming unstable intermediate. it has high activation energy barrier (high energy energy transition state)