Organic Chemistry I Reactions

Acid-catalyzed hydration of alkenes adds…

OH Markovnikov, typically yielding an alcohol product. This reaction INVOLVES carbocation rearrangements.

Reaction conditions for acid-catalyzed hydration of alkenes are…

H₂SO₄ (cat.), H₂O, and the alkene

Acid-catalyzed hydration of an alkene with an alcohol solvent creates…

an ether product, with the oxygen and its substituent adding Markovnikov.

Reaction conditions for acid-catalyzed hydration of alkenes with alcohol solvents are…

R-OH, HCl (cat.)

X₂ addition to alkenes adds…

X₂ anti across the double bond, often forming chiral or meso products. This reaction IS stereospecific, since the first halide added forms a bridged transition state.

Reaction conditions for X₂ addition to alkenes are…

X₂, CH₂Cl₂ (inert solvent)

HOX addition to alkenes forms…

a halohydrin, Markovnikov wrt/ OH, and the halide and OH add anti to each other.

Reaction conditions for HOX addition to alkenes are…

X₂, H₂O. Replacing water with an alcohol creates an ether in place where an alcohol would form with water.

Oxymercuration-reduction of alkenes adds…

OH Markovnikov, typically yielding an alcohol product. The first step is anti stereospecific, but the overall reaction is not. This reaction AVOIDS carbocation rearrangements.

Reaction conditions for oxymercuration-reduction of alkenes are…

1) Hg(OAc)₂, THF, H₂O
2) NaBH₄, H₂O

Hydroboration-oxidation of alkenes adds…

OH anti-Markovnikov, typically yielding an alcohol product. Addition of H and OH are syn stereospecific.

Reaction conditions for hydroboration-oxidation of alkenes are…

1) BH₃, THF

2) NaOH, H₂O₂, H₂O

Oxidation of an alkene to a glycol forms…

a cis-glycol (a 1,2-diol).

Reaction conditions for oxidation of an alkene to a glycol are…

OsO₄, H₂O₂, H₂O

Ozonolysis of an alkene forms…

a ketone and aldehyde, two ketones (non-cyclic), or a non-cyclic molecule from a cyclic reactant with ketone and/or aldehyde groups.

Conditions for ozonolysis of an alkene are…

1) O₃
2) (CH₃)₂S

Catalytic hydrogenation of alkenes adds…

two hydrogens syn across the double bond to form an alkane.

Reaction conditions for catalytic hydrogenation of alkenes are…

H₂, Pd/Pt/Ni (transition metal catalyst)

→ this is the ALKENE one

Alkylation of acetylide anions…

uses a very strong base to deprotonate a terminal alkyne, whose carbon chain can then be extended via addition of a haloalkane.

Reaction conditions for alkylation of acetylide anions are...

1) NaNH₂, NH₃
2) X-R (R = carbon chain; most ideal X is iodine)

An alkene can be turned into an alkyne by…

doubly dehydrohalogenating it; this typically involves two steps. The first forms a haloalkane, and the second uses very strong bases to deprotonate, and halogens leave during this step to form an alkyne (elimination).

Reaction conditions to create an alkyne from an alkene are…

1) X₂, CH₂Cl₂
2) NaNH₂, NH₃, H₂O

→ Alternatively, KOH, EtOH, Δ can be used for 2)

Electrophilic addition of X₂ to an alkyne forms…

a trans-alkene (1 eq.) or an alkyl halide with two halogens on each of the carbons of the former triple bond (2 eq.).

Reaction conditions for electrophilic addition of X₂ to alkynes are…

X₂, CH₂Cl₂ (1x or 2x depending on desired product)

Addition of hydrogen halides (HX) to alkynes forms…

a haloalkene (1 eq.) or an alkyl halide with two halogens on the more substituted carbon (2 eq.). This reaction is Markovnikov wrt/ X

Reaction conditions for HX addition to an alkyne are…

HX (1x or 2x depending on desired product)

Hydroboration-oxidation of an ALKYNE forms…

aldehydes, as this reaction is anti-Markovnikov. The starting reactant should be a terminal alkyne (1-alkyne), and the aldehyde forms from keto-enol tautomerization after formation of an enol via hydration.

Reaction conditions for hydroboration-oxidation of ALKYNES are…

1) (sia)₂BH, THF
2) H₂O₂, H₂O, NaOH

Acid-catalyzed hydration of ALKYNES forms…

ketones from 1-alkynes. This reaction is Markovnikov wrt/ OH, and rapidly converts into a ketone via keto-enol tautomerization.

Reaction conditions for acid-catalyzed hydration of ALKYNES are…

HgSO₄, H₂SO₄, H₂O

Catalytic reduction of ALKYNES forms…

an alkane by addition of 4 hydrogens (two to each carbon on either side of the triple bond).

Reaction conditions for catalytic reduction of ALKYNES are…

H₂, Pd/Pt/Ni (transition metal catalyst)

→ this is the ALKYNE one

Reaction conditions to form a cis-alkene from an alkyne are…

H₂, Lindlar’s catalyst

Reaction conditions to form a trans-alkene from an alkyne are…

H₂, Na, NH₃

Radical halogenation of alkanes forms…

a haloalkane by substituting one of the hydrogens for a halogen. This reaction involves HOMOLYTIC bond cleavage.

Reaction conditions for radical halogenation of alkanes are…

X₂, Δ or hv

Radical chlorinations are…

unselective, and the halogen will add to all possible positions. This reaction is EXOthermic, and the transition state has LITTLE radical character.

Radical brominations are…

highly selective, and one/few major products will form. This reaction is ENDOthermic, and the transition state has SIGNIFICANT radical character.

Allylic bromination adds…

bromine to allylic carbon(s). Transition states and products tend to favor the most stable alkene, not the most stable radical.

Reaction conditions for allylic bromination are…

NBS, Δ

Radical HBr addition to alkenes adds…

Br anti-Markovnikov (to the more accessible carbon).

Reaction conditions for radical HBr addition to alkenes are…

HBr, ROOR (a peroxide; radical initiator), Δ

This reaction tends to invert the configuration of chiral centers via backside attacks, and is concerted (single-step), often avoiding rearrangements…

S_N2

This reaction is often solvolytic, and forms a mixture of inverted and noninverted configurations of a chiral center. Rearrangements are possible due to formation of a carbocation intermediate…

S_N1

The best leaving groups for S_N1 AND S_N2 reactions are…

weak bases (I>Br>Cl>F in terms of best to worst). They should also not have an existing negative charge so one can be gained when bond electrons move onto this group.

The STRONGEST nucleophiles…

have accessible electrophilic carbons. They often also have negative charges.

S_N2 solvents should be…

polar and APROTIC; that is, there are NO H-bond donors (O-H or N-H bonds).

S_N1 solvents should be…

polar and PROTIC; that is, there ARE H-bond donors (O-H or N-H bonds).

S_N2 electrophiles should be…

easy to attack, with little steric hindrance

S_N1 electrophiles should be…

maximally substituted to form a more stable carbocation

Zaitsev products are…

MORE substituted elimination products

Hofmann products are…

LESS substituted elimination products

For an E2 reaction to occur, the leaving group and β-hydrogen must be…

anti and coplanar

During E2, SMALLER bases (ie. EtOH) produce…

primarily Zaitsev products.

During E2, LARGER bases (ie. LDA, BuOK) produce…

primarily Hofmann products.

For an E2 reaction to occur on a CYCLIC reactant, the leaving group and β-hydrogen must be…

axial and trans

Which reaction(s) occur if…

• Base is strong

• Nucleophile is weak

Or…

• Reactant is third-degree

• Base is strong

• Nucleophile is strong

Only E2

Which reaction(s) occur if…

• Reactant is first-degree

• Base is strong

• Nucleophile is strong

S_N2 and some E2

Which reaction(s) occur if…

• Reactant is first-degree OR second-degree

• Base is weak

• Nucleophile is strong

Only S_N2

Which reaction(s) occur if…

• Reactant is first-degree OR second-degree

• Base is weak

• Nucleophile is weak

No reactions occur

Which reaction(s) occur if…

• Reactant is second-degree

• Base is strong

• Nucleophile is strong

E2 and some S_N2

Which reaction(s) occur if…

• Reactant is third-degree

• Base is weak

• Nucleophile is weak

S_N1 and E1

Which reaction(s) occur if…

• Reactant is third-degree

• Base is weak

• Nucleophile is strong

Only S_N1

Examples of bulky, strong bases are…

KO-t-Bu, LDA

Examples of strong, NON-bulky bases are…

OH^- (obtainable from KOH, NaOH, LiOH…)

Examples of WEAK nucleophiles are…

H₂O, ROH, carboxylic acids (neutral!)

Examples of STRONG nucleophiles are…

Amines, NH₃, N₃^-, CN^-, etc. (negatively charged/anions!)

Active metal reactions…

deprotonate alcohols to form an alkoxide (an alkane with negatively charged oxygen).

Reaction conditions for active metal reactions are…

ROH, Na^o

HX reactions with alcohols form…

haloalkanes (via substitution) and sometimes alkenes (via E1)

Reaction conditions for HX-alcohol reactions are…

HX (and alcohol reactant)

Phosphorus tribromide reactions form…

R-Br from first and second-degree R-OH through a S_N2 mechanism. This reaction does not involve rearrangements, and configurations tend to invert.

Reaction conditions for phosphorus tribromide and alcohol reactions are…

PBr₃ (and alcohol reactant)

Thionyl chloride reactions form…

R-Cl from first and second-degree R-OH through a S_N2 mechanism. This reaction does not involve rearrangements, and configurations tend to invert.

Reaction conditions for thionyl chloride and alcohol reactions are…

SOCl₂, pyridine (and alcohol reactant)

Aryl and alkyl sulfonate reactions…

often substitute the hydrogen in the alcohol with another reactant (i.e. a tosyl group). This reaction is SOMETIMES S_N2.

Reaction conditions for aryl and alkyl sulfonate reactions usually are…

TsCl, pyridine

Acid-catalyzed dehydration of alcohols…

forms alkenes via elimination reactions; E2 in first-degree alcohols, and E1 in second and third-degree alcohols. This reaction typically favors Zaitsev products.

Reaction conditions for acid-catalyzed dehydration of alcohols are…

H₂SO₄, ∆ (and alcohol reactant)

Pinacol rearrangement of glycols…

forms carbonyl compounds. Rearrangements are common.

Reaction conditions for pinacol rearrangement are…

H₂SO₄ (cat.), H₂O, ∆, glycol reactant

Oxidation of FIRST-degree alcohols in the PRESENCE of water…

forms carboxylic acids (OH group is retained).

Reaction conditions for oxidation of first-degree alcohols to form carboxylic acids are…

H₂CrO₄ (chromic acid), H₂O

Oxidation of FIRST-degree alcohols in the ABSENCE of water…

forms aldehydes (OH group is not static; it reacts to form the aldehyde).

Reaction conditions for oxidation of first-degree alcohols to form aldehydes are…

PCC, CH₂Cl₂

Oxidation of SECOND-degree alcohols…

forms ketones, regardless of presence or absence of water.

Reaction conditions for oxidation of second-degree alcohols are…

H₂CrO₄, H₂O … OR … PCC, CH₂Cl₂

Periodic acid oxidation of glycols…

cleaves the bond between carbons bearing the OH groups, forming aldehydes and/or ketones.

Reaction conditions for periodic acid oxidation of glycols are…

HIO₄

To be oxidized by periodic acids, cyclic glycols must be…

a cis-isomer due to the formation of a cyclic periodate.

A haloalkane can be extended from the halogen’s position into a terminal alkyne under these conditions…

Na⁺, acetylide anion (-), DMSO