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Encyclopedia > Organic reactions

Organic reactions are chemical reactions between organic compounds.

Contents

Reactions, by function

The number of possible organic reactions is basically infinite. However, certain general patterns are observed that can be used to describe many common or useful reactions. Each reaction has a stepwise mechanism that says how it happens, although this detailed description of steps is not always clear from a list of reactants alone.


Organic reactions can be organized into several basic types:

  1. Addition reactions (halogenation, hydrohalogenation, halogenation, hydration)
    1. EA (electrophilic addition)
    2. NA (nucleophilic addition)
    3. RA (radical addition)
  2. Elimination reactions (dehydrohalogenation, dehydration)
    1. E1 elimination
    2. E2 elimination
  3. Substitution reactions
    1. SN1 substitution
    2. SN2 substitution
    3. ES (electrophilic substitution)
    4. EAS (electrophilic aromatic substitution)
    5. RS (radical substitution)
  4. Redox reactions
    1. Oxidation reactions
    2. Reduction reactions
  5. Condensation reactions (Nucleophilic addition + Elimination) and hydrolysis
  6. Polymerization reactions
    1. Addition polymerization
    2. Condensation polymerization
  7. Rearrangement reactions

Some reactions fit into more than one category. For example, some substitution reactions follow an addition elimination pathway.


Here are some common reactions that you may run into in a college organic chemistry course: addition of HX to an alkene, halogen addition reaction, halohydrin formation reaction, oxymercuration reaction, hydroboration-oxidation reaction, hydrooxylation reaction, ozonolysis reaction, nucleophilic substitution, halogenation of an alkyl, hydration and dehydration.


Here is a series of reactions that a chemist can perform to change molecules in a defined way: Beckmann rearrangement, Friedel-Crafts alkylation and acylation, Gilman reagent, Grignard reagent, Diels-Alder reaction, Pinner reaction, Sharpless epoxidation, Sharpless bishydroxylation, Swern oxidation


As seen here, specific reactions are sometimes named after the chemist who developed them.


(When adding to this page, if a reaction has a common name, please include it at the BEGINNING of the line, for consistency. If the reaction consists of multiple steps, include all steps on a single line, separated by a semicolon.)


Reactions, by reactants: aliphatic compounds

Hydrocarbons

Alkanes (R)

(RS) Free radical halogenation alkane + X2 --> alkyl halide + HX
Combustion alkane + O2 --> CO2 + H2O + heat
Cracking alkane  ?? --> 2 short alkanes

Alkenes (R=R), Dienes (R=R=R), and Alkynes (R≡R)

(EA) Catalytic addition of hydrogen (alkene or alkyne) + H2 /[Pt] --> alkane
(EA) Diels-Alder reaction conjugated diene + dienophile (in heat) --> cycloalkene
(EA) Alkylation (step 1...) terminal alkyne + strong base (:B-) --> acetylide ion
(...step 2) acetylide ion + alkyl halide --> longer alkyne
(EA) addition of HX to an alkene alkene or alkyne + hydrogen halide --> alkyl halide
(EA) alkene or alkyne + Cl2 or Br2 --> alkyl dihalide
(EA) alkene or alkyne + Cl or Br and hydroxide group --> alkyl halide (Markovnikov's rule)
(EA) oxymercuration reaction alkene in H2O / THF with Hg(OAc)2, and then with NaBH4, --> alcohol
(EA) hydroboration-oxidation reaction alkene or alkyne + B2H6/H2O --> alcohol
(EA) alkene or alkyne + water on an organo-mercury intermediate --> alcohol
- alkene + (KMnO4 or OsO4) and NaHSO3 --> diol
Cleavage alkyne + O3 or KMnO4 neutral or acidic solution --> 2 carboxylic acid
Cleavage alkene + ozone followed by zinc in acetic acid --> 2 ketones
Cleavage alkene + KMnO4 neutral or acidic solution --> either 2 ketones or carboxylic acid + ether
- alkene + ozone aldehyde (will cause the bond to break if there is a vinylic hydrogen)


(RS) Free radical bromination: alkene + N-bromosuccinaimide (NDS) -> brominated at allylic position, without addinng to double bond.


Hydrocarbons plus Group 17 (Halogen)

Alkyl halides (RX)

(SN1) alkyl halide + nucleophile -> nucleophile displaces the halogen atom
(SN2) alkyl halide + nucleophile -> nucleophile displaces the halogen atom
(E1) alkyl halide + base -> alkene (most substituted possible, Zaitsev's rule)
(E2) alkyl halide + base -> alkene (most substituted possible, Zaitsev's rule)
(SN2) Williamson ether synthesis alkoxide + alkyl halide ether
- Gilman reagent + alkyl halide + THF in basic solution --> larger alkane + LiBr
Heck reaction (aryl, benzyl, or vinyl) (halide or triflate) + alkene --> expanded carbon skeleton
Stille reaction (aryl, benzyl, or vinyl) (halide or triflate) + stannane --> expanded carbon skeleton
Suzuki reaction (aryl, benzyl, or vinyl) halide + organoborane in basic solution --> expanded carbon skeleton

Hydrocarbons plus Group 16 (Chalcogen)

Oxygen containing compounds

Alcohols (ROH) and Diols (HOROH)

  • Primary alcohols = SN2
  • Tertiary alcohols = SN1
  • Secondary alcohols = SN1 or SN2 (SNX)
Deprotonation alcohol + strong base --> alkoxide ion
Protonation alcohol + strong acid --> oxonium ion
(EX) dehydration tertiary alcohol acid catalyst --> alkene + H2O
(SN1) secondary alcohol + hydrogen halide heat -> alkyl halide
(EX) dehydration alcohol acid catalyst + heat <--> alkene + H2O
(EX) dehydration alcohol + POCl3/pyridine --> alkene + H2O
(SN1) tertiary alcohol acid catalyst --> alkyl halide
(SNX) alcohol + HBr heat --> alkyl halide (RBr)
(SNX) alcohol + HI heat --> alkyl halide (RI)
(SNX) alcohol + HCl ZnCl2/heat --> alkyl halide (RCl)
(SN2) 1 or 2 alcohol + PBr3 /pyridine --> alkyl halide (RBr)
(SN2) 1 or 2 alcohol + PCl3 /pyridine --> alkyl halide (RCl)
(SN2) 1 or 2 alcohol + SOCl2 /pyridine --> alkyl halide (RCl)
(SNX) alcohol + sulfonyl chloride (TsCl) -> ROT + sulfonate ester
- sulfonate ester --> compound with a new group bonded to the sp3 carbon
Oxidation primary alcohol or secondary alcohol + oxidizing agent --> carbonyl
Oxidation primary alcohol + oxidizing agent (such as pyridinium chloride) aldehyde
Oxidation secondary alcohols + oxidizing agent --> ketone
Cleavage 1,2-diol + HIO4/H2O --> 2 carbonyl
Transesterification ester + alcohol <---> different ester + different alcohol
- 2 alcohol ether
- alkene + alcohol acid catalyst ether

Ethers (ROR)

(SNX) Cleavage ether + HX heat --> alcohol + RX
(SN1) Cleavage tertiary ether acid catalyst --> alcohol + HX (stable)
(SN2) Cleavage primary ether or secondary ether acid catalyst --> alcohol + HX (unstable)

Epoxides (R2COCR2)

(SN1) ring-opening epoxide acid catalyst --> ring opened at most substituted position
(SN2) ring-opening epoxide base catalyst --> ring opened at least sterically hindered position
ring-opening epoxide + ? --> ring opened + alcohol
ring opening and rearrangement arene oxide + ? + ? --> ring opened + alcohol
(step 1...) RBr + Mg/diethyl ether -> RMgBr4 (Grignard reagent)
(...step 2) epoxide + Grignard reagent --> long alcohol

Carbonyl derivatives (RCO-)

Aldehydes and Ketones
SNX aldehyde or ketone + hydride ion or a carbanion -->  ???
SNX aldehyde or ketone + HCN -->  ???
SNX aldehyde or ketone + primary amine acid catalyst -->  ???
SNX aldehyde or ketone + secondary amine acid catalyst -->  ???
SNX aldehyde or ketone + alcohol or thiol acid catalyst -->  ???
- aldehyde or ketone + phosphorus ylide --> alkene
SNX an A, B unsaturated aldehyde or ketone + HCN/amine/carbanion --> added to the B carbon

Aldehydes only (RCOH)
Reduction aldehyde + reducing agent primary alcohols
Oxidation aldehyde + oxidizing agent (such as potassium permanganate, nitric acid, or chromium oxide) carboxylic acid
Oxidation aldehyde + Tollens' reagent (Ag2O in aqueous ammonia) carboxylic acids (without attacking carbon-carbon double bonds)
(step 1...) aldehyde + alcohol + acid or base hemiacetal
(...step 2) hemiacetal + alcohol acid catalyst acetal + water
- aldehyde + water geminal diols
- aldehyde + HCN cyanohydrins, R-C(H)(OH)(CN).
- aldehyde + Grignard reagent alcohol with a substituted group from the Grignard reagent
Wolff-Kishner reaction aldehyde + hydrazine C=O bond reduced to CH2
Nucleophilic addition (step 1...) aldehyde + nucleophile tetrahedral carbonyl addition compound
(...step 2...) aldehyde + ammonia or primary amine tetrahedral carbonyl addition compound
(...step 3...) tetrahedral carbonyl addition compound acid catalyst imine + water

Ketones only (RCOR)
Nucleophilic addition ketone + anion of terminal alkyne tetrahedral carbonyl addition compound (alkoxide)
(...step 2) alkoxide + aqueous acid hydroxyalkyne
Nucleophilic addition ketone + ammonia or primary amine tetrahedral carbonyl addition compound
(...step 2) tetrahedral carbonyl addition compound acid catalyst imine + water
Nucleophilic addition ketone + secondary amine tetrahedral carbonyl addition compound;
(...step 2) tetrahedral carbonyl addition compound acid catalyst enamine + water
Nucleophilic addition ketone + Grignard reagent magnesium alkoxide
(...step 2) magnesium alkoxide + aqueous acid tertiary alcohol
Nucleophilic addition ketone + organolithium reagent lithium alkoxide
(...step 2) lithium alkoxide + aqueous acid tertiary alcohol
Nucleophilic addition ketone + alcohol + acid or base hemiacetal + water;
(...step 2) hemiacetal + alcohol acid catalyst acetal + water; This is a carbonyl-protecting reaction.
Electrophilic addition ketone + electrophile resonance stabilized cation
Wittig reaction ketone' + phosphonium ylide oxphosphetane
(...step 2) oxphosphetane phosphine oxide + alkene
- ketone + water geminal diol
- ketone + thiol acid catalyst thioacetal + water
- ketone + hydrazine or derivative of hydrazine hydrazone
- ketone + metal hydride metal alkoxide salt
(...step 2) metal alkoxide salt + water alcohol
Keto-enol tautomerism ketone acid catalyst enol
(...step 2) enol + halogen α-haloketone
Reactions at an α-carbon ketone + aqueous deuterium + D+ or OD- catalyst ketone-d + HOD
Wolff-Kishner reaction ketone group + hydrazine methyl group
Clemmensen reduction ketone group + Zn(Hg), HCl methyl group

Carboxylic acids (RCOOH)
- Carboxyl group + amine groups peptide bond
- Carboxyl group + alcohol ester
Reduction carboxylic acid + LiAlH4 primary alcohol
Deprotonation by base (:B-) carboxylic acid + H2O/acid or base -->  ???
SNX carboxylic acid + hydride ion --> alcohol
SNX carboxylic acid + alcohol --> Acid catalyst ester
- carboxylic acid + thionyl chloride (SOCl2) --> acid chloride

Esters (R'-COOR")
Reduction ester + DIBAH aldehyde
SNX ester + H2O acid catalyst or base catalyst carboxylic acid + alcohol
SNX ester + alcohol acid catalyst or base catalyst different ester + different alcohol
SNX ester + amine -->  ???
SNX ester + hydride ion -->  ???
SNX ester + carbanion -->  ???

Acid halides (RCOX)
SRX acid halide + alcohol --> ester
SRX acid halide + amine --> amide
SRX acid halide + hydride ion (water) --> carboxylic acid
SRX acid halide + carbanion -->  ???

Amides (RCONR2)
nucleophilic attack amide + water acid catalyst or base catalyst --> carboxylic acid + secondary amine

Sulfur containing compounds

Thiols (RSH)

2 thiols + Hg2+ + Hg2+ -> RS-Hg-SR + 2H+
RS- + R'-Br -> RSR' + Br-

Sulfides/Thioethers (RSR)

sulfide + R'I -> RSR'R + I-
RSRR + Y- -> RY + sulfide

Hydrocarbons plus Group 15 (Pnictogen)

Nitrogen containing compounds

Amines (RNH2)

(SN2) Alkylation secondary amine + alkyl halide --> tertiary amine
(SN2) Nucleophilic attack amine + acid chloride or sulfonyl chloride -->  ???
Nucleophilic addition (step 1...) ketone or aldehyde + ammonia or primary amine tetrahedral carbonyl addition compound
(... step 2) tetrahedral carbonyl addition compound acid catalyst imine + water

Imines (RC=N)

Nucleophilic addition: (step 1...) imine + (ammonia or primary amine) tetrahedral imine addition compound
(...step 2) tetrahedral imine addition compound acid catalyst new imine

Nitriles (RC≡N)

Phosphorus containing compounds

Reactions, by reactants: aromatic compounds

Benzene

(EAS) Friedel-Crafts alkylation  ?? + ?? -->  ??
(EAS) Friedel-Crafts acylation  ?? + ?? -->  ??
(EAS) Halogenation  ?? + ?? -->  ??
(EAS) Nitration  ?? + ?? -->  ??
(EAS) Sulfonation  ?? + ?? -->  ??

External Links

  • Organic reaction flashcards from OSU (http://www.chemistry.ohio-state.edu/organic/flashcards/)
  • list of named reactions from UConn (http://orgchem.chem.uconn.edu/namereact/named.html)

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