Unformatted text preview:

Exam 5 Study Guide!!Chapter 21: Amines!I. Naming !1. Substituted Amines: # of groups on N !!!!!!!2. As alkanamines (N-alkyl amines) !!!!!!!!!!!!!!!!3. As amino substituents !!!!!4. As alkyl amines !!!!!!II. Nucleophilicity and Basicity !1. Amines are good nucleophiles and bases !A. Lone pair on N can act as a nucleophile by attacking an electrophile !!!!!!!B. Lone pair on N can act as a base by grabbing a proton !!!!!!!!-more steric hinderance leads to greater basicity (except tertiary) !!!!!!!2. Amides are formed from deprotonated primary and secondary amines!!!!!-stronger nucleophiles and bases than neutral amines !!!!!!!!!3.Alkyl vs. Aryl Amines !A. Alkyl Amine - N is attached to an alkyl group !!!!!B. Aryl Amine - N is attached to an aromatic ring !!!!!-less nucleophilic and basic than alkyl amines because lone pair is delocalized into the aromatic ring !!!!!!!!!III. Synthesis of Amines !1. Alkylation of Amines !A. Direct alkylation (through SN2) leads to polyalkylations !!!!!!-this does multiple alkylation because the product is still nucleophilic and will react again with the electrophile!!B. Indirect alkylation is required for monoalkylations !-Cyanide Displacement Reduction !!!!!-Azide Displacement Reduction !!!!!!!!-Gabriel Synthesis (primary amines from primary alkyl halides) !!!!!!!!!-mechanism!!!!!!!!!!!!!!!!!*works best with primary alkyl halides as it relies on SN2 reaction. Secondary alkyl halides work but not as well as primary and tertiary alkyl halides do not work at all. Also, it will not work for aryl halides. !!2. Reductive Amination - forming an amine from an imine via reduction !!!!!!!A. This is useful because the starting material is an aldehyde or ketone and we know many ways to makes them. !!3. Preparation of Amines from Carboxylic Amides!A. Reduction with LAH !!!!!!B. Hoffman Rearrangement !!!!!!-this involves a loss of one carbon atom !-useful because it gives us a way to make an amine from any carboxylic acid derivative !!!!!IV. Reactions of Amines !1. Acylation of Amines !-converting an amine into an amide!!!!!!!**the addition and removal of an acyl group to an amine can be useful in synthesis problems. The addition of this group can turn a strong activator into a moderate activator. For example, imagine you want to make this: !!!!!!!The problem is the amino group is TOO strong of an activator group and will lead to unwanted products. Therefore, by adding an acyl group to the amine and then adding nitric acid we can get our desired product. !!!!!!!!!2. Hoffman Elimination !A. Elimination of tetraalkylammonium hydroxides !!!!!!B. Gives least stable alkene (anti-zaitsev TS) !!Anti-Zaitsev !!!!Zaitsev!!!!3. Mannich Reaction !-enol + iminium!!!!!!!!-mechanism !!!!!!!!!!!!!!4. Nitrosation !-amines react with nitrosyl cations (NO+) !!A. Nitrosyl cation formation (NaNO2 +HCl) !!!!!!!!!!!!B. Tertiary Amine Attack !!!!!!!C. Secondary amines lead to N-nitrosamines!!!!!!D. Primary amines lead to carbocations!!!!!!!!!!!!!Chapter 22: Benzene Substituents!I. Reaction at the Benzyl Position !!!!!1. Radical Halogenation !!!!!!2. Solvolysis (SN1) !!!!!!3. SN2!-100x faster/more reactive than primary sp3!!!!!!4. Acidity of Benzylic Hs!!!!!!!!5. Oxidation !A. Oxidative cleavage of alkyl groups !!!!!!!-must have at least one benzylic H!!!!!!-the second benzylic position will undergo oxidation if the reaction is allowed to react for a long time !!B. Selective Benzylic Oxidation of OHs!!!!!!!!6. Reduction of the Benzylic Carbon !!!!!!!!!7. Benzyl Ethers as Protecting Groups !!!!!!!!!II. Phenols !!!!!!!-conjugate base is resonance stabilized !!!!!1. Preparation of Phenols !A. Nucleophilic Aromatic Substitution (NAS) !!!!!!!!-NO2 is a strong deactivating group and electron withdrawing!-this reaction will not go through SN2 as there's no backside attack available and it will not go through SN1 because the ring is very high in energy!!-Would go by addition/elimination mechanism !!!!!!!!- Mechanism Idea !Rate of Formation (NaOCH3) !F = 312 (small and electronegative) !Cl = 1.0!Br = 0.8!I = 0.4 (best LG) !!!!!!!!!!!2. NAS - Benzyne (elimination/addition) !-do not need electron withdrawing groups!-need very extreme conditions for reaction to occur !!!!!!!!!!!!A. Example - label using carbon-14!!!!!!!3. Aryl Diazonium Ions !!!!!!!!!!!!!!!!!A. Mechanism !-nitrosyl cation formation !!!!!!!-mechanism !!!!!!!!!!B. Diazonium Ions as Electrophiles in EAS Reactions !!!!!!!!-mechanism !!!!!!!!!!!!III. Reactions of Phenols !1. Acidic Cleavage of Aryl Ethers !!!!!!!A. Mechanism !!!!!!!2. Formation of Ethers !!!!!!A. Mechanism !!!!!!3. Phenols as Nucleophiles in EAS !!!!!!!A. Phenol is a strong activator, sometimes can observe multiple additions of electrophile !!!4. Base-Mediated Substitution !!!!!!!!!!!!!!IV. Electrocyclic Reactions !1. Claisen Rearrangement !!!!!!!A. Mechanism!!!!!!!!2. Cope Rearrangement !!!!!!!!A. Claisen Rearrangement !!!!!!!!- C=O stability makes equilibrium lie to the right!- proceeds through chairlike TS !!V. Benzoquinones !1. Radical Oxidation of Phenols !!!!!!!!!!2. Reactions of Benzoquinones !!!!!!!!!!!!!!!!VI. Biological Reactions !-certain vitamins can stabilize free radicals !!!!!!!!!!!!!!!!!!!-all has to do with resonance stability !!!Chapter 15: Heterocycles !I. Naming !1. Named as heterocycloalkanes !-aza (N), oxa (O), thia (S), phospha (P)! !!!!2. Common names to memorize**!!!!!!!II. Reactivity of Nonaromatic Heterocycles !1. 5+ membered rings (unreactive towards nucleophiles) !-usually used as bases and solvents !!!!!2. 3- & 4- membered rings undergo ring opening !!!!!!!-ring strain drives this reaction!-Nucleophile attacks the least substituted side because of sterics and basic conditions !!!!!!!-proceeds through carbocation TS!-Nucleophile attacks more substituted side due to acidic conditions !!III. Properties of 5-Membered Aromatic Heterocycles !1. Aromaticity and Electron Count !!!!!!-only one lone pair counts towards aromaticity!-remember: 4n + 2 is aromatic !!!!!!!!!!!!!!-more electronegative atoms are less aromatic (S>N>O) !-other heteroatoms do not contribute to resonance !!!Neutral sp2, lone pairs do NOT contribute to resonance !!Neutral sp3, lone pairs DO contribute to resonance !!2. General Synthesis: Paal-Knorr!!!!!!Conditions X!R-NH2 N-R!P2O5 O!P2S5 S!!A. Example!!!!!!!-for synthesis problems, can add different R groups to the ends of the


View Full Document
Download Exam 5 Study Guide
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Exam 5 Study Guide and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Exam 5 Study Guide 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?