Organic Chemistry Reactions Flashcards
What is the rate law for an SN2 reaction?
An SN2 reaction is bimolecular. The rate depends on both the substrate and the nucleophile. The formation of the transition complex (which involves both the substrate and the nucleophile) is the rate-limiting step.
What is the rate law for an SN1 reaction?
An SN1 reaction is unimolecular. The rate depends on just the substrate. Specifically, the formation of the carbocation is the rate-limiting step.
What type of solvents are best suited for an SN1 reaction? Why?
Polar protic solvents are best for SN1 reactions. This is becuase they help stabilize carbocations, and aid in removal of the leaving group.
Below are the most common polar protic solvents
Examples of polar protic solvents: alcohols, carboxylic acids, ammonia, Bronsted acids (typically aqueous), and of course water.
What type of solvents are best suited for an SN2 reaction?
Polar aprotic solvents are best for SN2 reactions, which allow for the nucleophile to react with the substrate without interacting with the solvent.
Below are the most common polar aprotic solvents
Examples of polar aprotic solvents: acetone, dimethyl sulfoxide (DMSO), ethers, alkane (i.e. hexane), and chloroform.
For an E2 reaction, what orientation must the substrate be in?
The leaving group and cleaved proton must be anti-coplanar in respect to one another.
List the thermodynamic stability trend for alkenes
Unsubstituted < monosubstituted < cis-disbustituted < trans-disubstituted < trisubstituted < tetrasubstituted
For an E2 reaction, why do we consider the thermodynamic stability of the product?
The most thermodynamically stable product (the Zaitsev product) will be favored when using a nonbulky base (minimizing steric hindrance) and the less thermodynamically stable alkene (the Hoffman product) will be formed when using a bulky base.
List the stability trend for carbocations
The alkyl groups around a carbocation will help stabilize the positive charge due to their positive inductive effect (increasing electron density at the carbocation center). Also, remember that mesomeric effects (resonance stabilization) is stronger than inductive effects.
What is the rate-limiting step for an SN1 reaction?
The formation of the carbocation
What is a Lewis base?
A substance that can donate a pair of nonbonding electrons (such as the lone pair of an oxygen or nitrogen atom). Many Lewis bases are utilized for this chemical trait due to their nucleophilicity.
What is a Lewis acid?
A substance that can accept an electron pair (an electrophile) due to a vacant orbital. Many cationic metals are Lewis acids (Ag+</sub>,Cu+, Al3+), also a common Lewis acid is BF3.
What is a nucleophile?
A molecular or atomic species that can attack a nucleus (nucleophile - nucleus loving) typically a positively charged or partially positive center.
What is the rate-limiting step for an E2 reaction?
The formation of the transition-state complex.
What is an electrophile?
Electrophiles are chemical species that are attract/attracted to electron dense species (electrophile - electron loving).
How does a positive inductive effect impact the acidity of a carboxylic acid?
Will the pKa increase or decrease?
The pKa will increase, the positive inductive effect will increase the electron density of the O-H bond and consequently strengthen the bond (decreasing the acidity).
How does a positive inductive effect impact the acidity of a carboxylic acid?
Will the pKa increase or decrease?
The pKa will decrease, the negative inductive effect will decrease the elctron density of the O-H bond, weaknening the bond so that the proton is more likely to dissociate (becoming more acidic).
