organic chemistry 4: analyzing organic reactions

[...] acids are electron acceptors

lewis acids

• contains vacant orbitals or postive polarized atoms

• lewis acids are electron acceptors

[...] bases are electron donors

lewis bases

• contain a lone pair of electrons and are often anions

A/an [...] acid is a proton donor

Bronsted-Lowry acid

A/an [...] base is a proton acceptor

A/an Brønsted-Lowry base is a proton acceptor

[...] molecules can act as either acids or bases

amphoteric

K_a is the [...] constant

acid dissociation

• an indicator of acid strength

• it is the equilibrium constant corresponding to the dissociation of an acid, HA into a proton and its conjugate base

Low pK_a = [weak or strong] acid

strong

A/an [...] reaction is a reaction with the transfer of electrons from the substance being oxidized to the substance being reduced

redox

[...] is the charge an atom would have if all its bonds were completely ionic

oxidation number

In REDOX reactions, the [oxidized or reduced] molecule loses electrons and the oxidation number increases

oxidized

An oxidizing agent [accepts or donates] electrons and is [oxidized or reduced] in the process

accepts; reduced

n REDOX reactions, the [oxidized or reduced] molecule gains electrons and the oxidation number decreases

reduced

A reducing agent [accepts or donates] electrons and is [oxidized or reduced] in the process

donates

oxidized

[...] is the ability of a reagent or inter­mediate to react with one group or atom in a mole­cule in preference to another group or atom present in the same molecule

chemoselectivity

A/an [...] contains lone pairs of electrons or pi bonds and is “Nucleus-loving”

nucleophile

[...] is a term used to describe the strength of a  nucleophile

nucleophilicity

• nucleophilicity is affected by:

  • charge

  • electronegativity

  • steric hindrance

  • solvent

[...] are electron loving

electrophiles

• contain a positive charge or are positively polarized

[...] are molecular fragments that retain the electrons after heterolysis

leaving groups

• the least LG can stabilize additional charge through resonance of induction

• weak bases make good leaving groups

Cl^- and Br^- are [good or bad] leaving groups

good

-OH is a[good or bad]leaving group

bad

The "S_N" in S_N1 and S_N2 reactions refers to [...]

nucleophilic substitution

The number 1 in an S_N1 reaction refers to the fact that the reaction is [...]

unimolecular

SN1 rate = k(substrate)¹ = a first-order reaction

An S_N1 reaction has [#] step(s)

two

step 1: the LG leaves, forming a carbocation

step 2: the nucleophile attacks the planar carbocation from either side, leading to a racemic mixture of products

An S_N2 reaction has [#] step(s)

one

• the nucleophile attacks at the same time as the lG leaves

• the nucleophile must perform a backside attack, which leads to inversion of stereochemistry

[S_N1 or S_N2] products are a racemic mixture

SN1

• in the 2nd step, the nucleophile attacks the planar carbocation from either side, leading to a racemic mixture of products

[S_N1 or S_N2] reactions lead to inversion of stereochemistry

SN2

• the nucleophile must perform a backside attack, which leads to inversion of stereochemistry

The rate law for an S_N1 reaction is [...]

S_N1 Rate = k[substrate]¹

 

A first-order reaction

The rate law for an S_N2 reaction is [...]

S_N2 Rate = k[substrate]¹[nucleophile]¹

 

A second-order reaction

A primary substrate will go [S_N1 or S_N2]

Sn2

1 step: if you were do an do an sn1 reaction on a primary substrate you’d get a primary carbocation which is very unstable

A tertiary substrate with a protic (or aprotic) solvent will go [S_N1 or S_N2]

sn1

2 steps

• there is to much steric hinderance for the nucleophile to attack the carbon while the leaving group is still there. The LG must leave first

• the products will be a mixture of sn1 and e1

theis reaction will go

sn1

the substrate is secondary to CH3OH is a protic solvent

this reaction will go

sn2

the substrate is secondary and acetone is an aprotic solvent

S_N2 reactions prefer[...]substrates

methyl and primary

it is easy for the nucleophile to attack the carbon because the carbon is accessible (less steric hindrance)

the reaction can process in 1 step

A methyl substrate cannot undergo an elimination reaction because elimination reactions create [...]

double bonds between two carbons, C=C

there is only one carbon in methyl so no double bond can be created

Strong bases favor [...] reactions

E2

A secondary substrate with a protic solvent will go [S_N1 or S_N2]

Sn1

A secondary substrate with an aprotic solvent will go [S_N1 or S_N2]

sn2

Polar [protic or aprotic] solvents are capable of hydrogen bonding

protic

• Polar Protic: Acetic Acid, H₂O, ROH, NH₃

Polar [protic or aprotic] solvents do not participate in hydrogen bonding

aprotic

• Polar Aprotic: DMF, DMSO, Acetone, Ethyl Acetate

Acetic acid is polar [protic or aprotic] 

protic

• polar protic because it participates in hydrogen bonding

DMSO is polar [protic or aprotic] 

aprotic

-dimethyl sulfoxide is polar aprotic because it does not participate in hydrogen bonding