Salt Lake Community College Department of Chemistry/Valcarce
Organic Reactions from O-Chem 2310 Review
The following are the substitution, addition and elimination reactions were covered
in organic chemistry 2310. To be successful in organic chemistry 2320 students
should be very familiar with these 23 reactions.
Substitution Reactions
We have three substitution reactions we learned in Chemistry 2310 and they all
involve substitution on a sp3 hybridized carbon:
Inorganic substitution
A highly efficient method of converting of alcohols to alkyl halides uses one of three inorganic
reagents:
sp3 hybridized carbon SOCl2
C Cl
alkyl chloride
PBr3
C OH C Br
alkyl bromide
alcohol PI3
C I
alkyl iodide
Mechanism Notes:
• No mechanism will be required for these inorganic substitution reactions.
• Stereochemistry will not be considered with these reactions.
• Inorganic substitution reactions do not undergo rearrangement.
Nucleophilic Substitution (Sn Substitution)
All Sn reaction reactions follow the following format:
sp3 hybridized carbon
C LG + :NUC C NUC + :LG
substrate product
The Leaving Group (LG) can be The Nucleophile (NUC)
any halide (-I, -Br, -Cl, or -F) or
can be anionic (-:NUC) or
Tosylate (-OTs) and any
protonated oxygen (-OR2+) Neutral (:NUC)
H
Mechanism Notes:
There are two mechanisms for Sn substitution reactions::
page 1
, Salt Lake Community College Department of Chemistry/Valcarce
Sn2 Sn1 (via carbocation)
• Sn2 is a bimolecular process for unsubstituted, • Sn1 is a unimolecular process for 3° or
1° and 2° substrates. allylic substrates or anytime a rearrangement
• Sn2 prefers polar aprotic solvents. has occurred.
• Stereochemistry by inversion of configuration • Sn1 will only occur in polar protic solvents
• No Rearrangements can occur in Sn2 reactions • Stereochemistry by inversion and retention
of configuration (you get both R and S
chiral centers).
• Rearrangements can occur in Sn1 reactions
Free-Radical substitution (bromination of alkanes)
Free radical halogenation of alkanes is an exceedingly important substitution reaction and forms
alkyl halides from alkanes. This substitution reaction replaces the hydrogen that allows the most
stable alky free-radical intermediate to form. This reaction works with chlorine and bromine,
but we will only use bromine in this class
Hydrogen that will
form the most stable
alkyl free-redical
intermediate. X2
C H C X + HX
heat or light
X = Cl, Br
alkane alkyl halide
Mechanism Notes:
• The most important step in the mechanism for free-radical substitution is the Alkyl
Radical Formation step:
Br + H C C + HBr
most stable alkyl
radical that can from.
In this step, we only extract the hydrogen that can form the most stable alkyl free-
radical intermediate that can form. The order of preference is allylic free-radical > 3°
free-radical > 2° free-radical > 1° free-radical > unsubstituted free-radical
• Stereochemistry will not be considered with these reactions.
• Free radical halogenation reactions do not undergo any rearrangement.
If you would like more details about these substitution reactions, please visit the
following Organic Chemistry 2310 supplement: Substitution Reactions Part II
Alkene Addition Reactions
There are nine alkene addition reactions we learned in Chemistry 2310 and they all
involve breaking the pi bond of an alkene. These reactions all release heat
(exothermic):
page 2
Organic Reactions from O-Chem 2310 Review
The following are the substitution, addition and elimination reactions were covered
in organic chemistry 2310. To be successful in organic chemistry 2320 students
should be very familiar with these 23 reactions.
Substitution Reactions
We have three substitution reactions we learned in Chemistry 2310 and they all
involve substitution on a sp3 hybridized carbon:
Inorganic substitution
A highly efficient method of converting of alcohols to alkyl halides uses one of three inorganic
reagents:
sp3 hybridized carbon SOCl2
C Cl
alkyl chloride
PBr3
C OH C Br
alkyl bromide
alcohol PI3
C I
alkyl iodide
Mechanism Notes:
• No mechanism will be required for these inorganic substitution reactions.
• Stereochemistry will not be considered with these reactions.
• Inorganic substitution reactions do not undergo rearrangement.
Nucleophilic Substitution (Sn Substitution)
All Sn reaction reactions follow the following format:
sp3 hybridized carbon
C LG + :NUC C NUC + :LG
substrate product
The Leaving Group (LG) can be The Nucleophile (NUC)
any halide (-I, -Br, -Cl, or -F) or
can be anionic (-:NUC) or
Tosylate (-OTs) and any
protonated oxygen (-OR2+) Neutral (:NUC)
H
Mechanism Notes:
There are two mechanisms for Sn substitution reactions::
page 1
, Salt Lake Community College Department of Chemistry/Valcarce
Sn2 Sn1 (via carbocation)
• Sn2 is a bimolecular process for unsubstituted, • Sn1 is a unimolecular process for 3° or
1° and 2° substrates. allylic substrates or anytime a rearrangement
• Sn2 prefers polar aprotic solvents. has occurred.
• Stereochemistry by inversion of configuration • Sn1 will only occur in polar protic solvents
• No Rearrangements can occur in Sn2 reactions • Stereochemistry by inversion and retention
of configuration (you get both R and S
chiral centers).
• Rearrangements can occur in Sn1 reactions
Free-Radical substitution (bromination of alkanes)
Free radical halogenation of alkanes is an exceedingly important substitution reaction and forms
alkyl halides from alkanes. This substitution reaction replaces the hydrogen that allows the most
stable alky free-radical intermediate to form. This reaction works with chlorine and bromine,
but we will only use bromine in this class
Hydrogen that will
form the most stable
alkyl free-redical
intermediate. X2
C H C X + HX
heat or light
X = Cl, Br
alkane alkyl halide
Mechanism Notes:
• The most important step in the mechanism for free-radical substitution is the Alkyl
Radical Formation step:
Br + H C C + HBr
most stable alkyl
radical that can from.
In this step, we only extract the hydrogen that can form the most stable alkyl free-
radical intermediate that can form. The order of preference is allylic free-radical > 3°
free-radical > 2° free-radical > 1° free-radical > unsubstituted free-radical
• Stereochemistry will not be considered with these reactions.
• Free radical halogenation reactions do not undergo any rearrangement.
If you would like more details about these substitution reactions, please visit the
following Organic Chemistry 2310 supplement: Substitution Reactions Part II
Alkene Addition Reactions
There are nine alkene addition reactions we learned in Chemistry 2310 and they all
involve breaking the pi bond of an alkene. These reactions all release heat
(exothermic):
page 2
