CHEM322 Reactants and Reactions

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SOCl₂

• only reacts with carboxylic acids

• replaces an alcohol group with a chlorine

mCPBA

• forms epoxides

• forms esters from ketones (Baeyer-Villiger)

• forms carboxylic acid from aldehydes

HNO₂ , HCl

• performs a nucleophilic attack, then a deprotonation to form a diazonium salt

• good for multistep synthesis; in a reaction, releases N₂ (g), which is very stable

PCC

• mild oxidizing agent

• converts primary alcohols to aldehydes

• converts secondary alcohols to ketones without further oxidation

• does NOT work on tertiary or quaternary

• does not react with ketones or aldehydes

H₂CrO₄

• strong oxidizing agent

• converts primary alcohols to carboxylic acids

• converts secondary alcohols to ketones

• does not react with tertiary alcohols (all steps reversible) or quaternary

• converts aldehydes into carboxylic acids

• does not react with ketones

HgSO₄, H₂SO₄ and H₂O

• forms a ketone from an alkyne (catalyzed hydration)

• Hg²⁺ can make an epoxide

• H₂O breaks the epoxide

H⁺, H₂O

• converts alkenes to alcohols

• converts alkynes to enols which rearrange to ketones

a) BH₃ b) HOO^-

• performs concerted addition (anti-Markovnikov)

• forms alcohol from an alkene (hydroboration/oxidation)

a) Hg(OAc)₂ b) NaBH₄

• adds alcohol to most substituted carbon (Markovnikov)

• Alkene hydration

EtOH (or CH₃CH₂OH), H⁺

• performs alcohol addition

• turns ketones into acetals/ketal (requires 2 EtOH)

• turns double bonded oxygens into hemiacetals

What can turn a ketone into a hydrate?

Water (H+, OH-)

• can happen in acidic or basic conditions

CH3CH2NH2 with H₂O, H⁺

• forms imine from an aldehyde or ketone and a primary amine (all steps reversible)

• forms enamine from an aldehyde or ketone and a secondary amine (all steps reversible)

• Opposite direction is hydrolysis (see picture)

a) Hb(Sia)₂ b) HOO^-

• converts a terminal alkyne to a terminal aldehyde (hydroboration of alkynes)

• Anti-Markovnikov

a) PPh₃ b) Strong Base

• Wittig reaction

• AB + CD → AD + CB

• concerted addition (1 step)

• adds R group from PPh₃ to original molecule

• if symmetrical, stereochemistry does not matter

• if not symmetrical: non-stabilized = Z alkene, stabilized = E alkene

H₂NNH₂, base, heat

• Wolff-Kishner reduction (same product as Clemmensen reduction)

• reduces ketones to alkanes

• under basic conditions

Zn/Hg, HCl, H₂O

• Clemmensen reduction (same product as Wolff-Kishner reduction)

• reduces ketones to alkanes

• under acidic conditions

P₂O₅

• with two carboxylic acids, forms anhydride

What does a carboxylic acid and CH₃CH₂SH form?

a thioester

DCC, RNH₂

• forms amide from a carboxylic acid (DCC coupling)

• stops amine from taking H⁺ from carboxyl

What reagent is used in decarboxylation?

Heat

Which alcohol position does NaBH₄ and H⁺ work on in nucleophilic addition?

primary

Which alcohol position does LiAlH₄, RMgBr, and H⁺ work on in nucleophilic addition?

secondary

Which alcohol position does RLi and H⁺ work on in nucleophilic addition?

tertiary

a) O₃ b) DMS

• splits pi bonds

• add double bonded O to each side of original pi bond

• can perform cycloaddition/reversion reactions

How are cyclic acetals formed?

When a ketone reacts with a diol

What type of reaction is the reverse of acid-catalyzed hydrolysis?

Fischer esterification

Are all steps of base catalyzed hydrolysis reversible?

No, the last two steps are one way

KMnO₄, KOH, heat

• permagnate oxidation

• works on primary, secondary, tertiary

• does not work on quartnerary

• can form carboxylic acids on ‘benzylic’ positions (1 position away from aromatic ring)

a) EtMgBr b) H⁺ with a ketone

1,2 addition

a) CH3MgBr b) H⁺ with an enone

1,2 addition

a) Et₂CuLi b) H⁺ with an enone

1,4 addition (Michael’s addition)

a) Et₂CuLi b) H+ with a ketone

no reaction

What does excess CH2CH3SH and a carboxylic acid form?

a thioester

HgCl₂, H₂O

• turns S-H carbon chain groups back into ketones or aldehydes

• reverse reaction is thioacetal formation

a) LiAlH₄ b) H⁺

• converts aldehydes and ketones to alcohols

• reduces amides to amines (acidic conditions)

• forms aldehydes from esters

excess H₂O, H⁺

• acetyl hydrolysis

• converts acetyl to ketone

What does H₂CrO₄ do with a ketone?

Nothing; no reaction

What does PCC do with a ketone/aldehyde?

Nothing; no reaction

a) CO₂ b) H⁺ with a Grignard

• forms a carboxylic acid

What is the migratory rule (relating to Baeyer-Villager Oxidations)?

H > tertiary carbon > secondary carbon, Ph > primary carbon > methyl

-relevant when reacting mCPBA with asymmetrical ketones

What are the differences between LiAlH₄ and NaBH₄

Hg²⁺, H₂O

• forms ketones and aldehydes

• keto-enol tautomerization

^-OH, H₂O

• keto-enol tautomerization (base-catalyzed)

  • occurs via enolates

  • reversible

  • forms enols from ketones and vice versa

• reacts with ketones and aldehydes

a) LDA

b) ketone or aldehyde

c) H⁺, cold

• adds carbon chain

• leaves OH group where double bonded O was

a) LDA

b) ketone or aldehyde

c) H⁺, hot

• adds carbon chain

• removes alcohol group to form carbon pi bond

a) enolate

b) H⁺

• adds enolate at end of double bond

a) CH₃CH₂O^-

b) Carbon chain with halogen

• removes most acidic H

  • forms double bond where acidic H was

• cation adds to double bond

H₂, Lindlars

• makes z alkenes from alkynes

H₂, Pd

• removes pi bonds

• reduces anything to an alkane

H₂, Pt or Zn, HCl

• nitro reduction

• changes NO₂ group to NH₂

• replaces O₂ with hydrogens

• reduces alkynes to alkenes

Li, NH3 (Birch’s reduction)

• makes symmetrical pi system on aromatic ring

a) OsO₄ b) HO^- or NaOH, H₂O

• adds 2 alcohol groups onto either side of the double bond

• reduces double bond to alkane

Li, NH₃

• makes E alkenes from alkynes

• trans-conformations

• Na, NH₃ can also be used

PdL₄

• replaces halogen with carbon chain containing double bond

• organometallics

L₂PdCl₂, Cu/Et₂NH (any base)

• replaces halogen with carbon chain containing triple bond

• organometallics

Pd₂L₄ or NiL₄ (Negishi)

• replaces halogen with carbon chain only with single bonds

• organometallics

What are the three reactants in a Diels-Alder reaction?

• dienophile

• diene

• heat

see image for stereochemistry explanation

HNO₃, H₂SO₄

• adds NO₂ group to sp² hybridized carbon

What pi electron counts are associated with heat or light?

• 4n = light

• 4n + 2 = heat

What pi electron counts and rotations are associated with heat or light?

• 4n, disrotatory (turn in different directions) = light

• 4n, conrotatory (turn in same direction) = heat

• 4n + 2, disrotatory (turn in different directions) = heat

• 4n + 2, conrotatory (turn in same direction) = light

What pi electron count is associated with aromatic or antiaromatic?

• 4n + 2 = aromatic

• 4n = antiaromatic

• anything else is nonaromatic

• rings must be conjugated to be antiaromatic/aromatic!

The ortho/para positions are associated with what type of groups?

EDG (electron donating groups)

The meta position is associated with what type of groups?

EWG (electron withdrawing groups)

SO₃ , concentrated H₂SO₄

• adds to para position only when dealing with EDGs

• adds SO₃H to the para position

dilute H₂SO4, excess H₂O

removes SO₃

Br₂, FeBr₃

• electrophilic aromatic substitution

• adds to aromatic ring on sp² carbon

• other halogens can be used instead of Br (ie: Cl)

Cl₂, AlCl₃

• will chlorinate and add any R group/carbon substituent, knocking off the Cl

  • if the Cl has no R group, it is the only one added

List the protecting groups

• TIPS

• TMS

• TDS

• TES

• TBS

• TBDPS

• should all be paired with a leaving group (ie: halogen)

What is the function of protecting groups and how can they be removed?

• expose other groups on the compound

• deprotectors/removers: HF, TBAF, NaF

  • anything with fluorine

HBr

• Markovnikov

• adds Br (brominates) most substituted carbon in double bond

• acts in absence of light or peroxides

Br₂, light

• adds Br to benzylic or allylic position

• if performing allylic bromination, Br₂ concentration must be low or else Br will be added on either side of the double bond

HBr, ROOR, light

• anti-Markovnikov

• Br attaches to least substituted carbon in a double bond

KOH (alc), heat

• creates alkene from alkane

KOH, heat (200 degrees)

• double elimination

• dehalogenates

• creates alkynes from alkanes

NaH

• super base

  • stronger than NaOH

• used to deprotonate alcohols

• can be used in Williamson ether synthesis