CHM 234| Nucleophilic Substitution and Ketone and Aldehyde
CHM 234| Nucleophilic Substitution and Ketone and Aldehyde CHM 234
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This 9 page Class Notes was uploaded by Alvin Notetaker on Monday April 11, 2016. The Class Notes belongs to CHM 234 at Arizona State University taught by Pillai in Fall 2015. Since its upload, it has received 9 views. For similar materials see General Organic Chemistry II in Chemistry at Arizona State University.
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Date Created: 04/11/16
Nucleophilic Aromatic Substitution Need: ● Strong Nucleophile ● Strong electron withdrawing group ● Must be in the ortho or para position to the withdrawing group. Mechanism: Example: Chapter 20: Aldehyde and Ketone Aldehyde: Nomenclature: 1. Find parent chain 2. Find substituents 3. Assign a number to each substituents 4. Arrange it alphabetically 5. Aldehyde carbon is position 1 6. ICPAC: Replace e with al 3chlorobutanal Hexanedial As of right now, aldehyde functional group will have the utmost priority. A cyclic compound with an aldehyde group adjacent to it is called carbaldehyde . Example: Cyclohexanecarbaldehyde Ketone: Nomenclature: 1. Has to be the lowest number 2. ICPAC: Replace e with one 3hexanone / ethyl propyl ketone 2,4pentanedione Acetophenone / methyl phenyl ketone Carbonyl as Substituent ● Aldehydes have a higher priority than ketone. ● Substituent names for: ○ Ketone = oxo ○ Aldehyde = formyl 4oxopentanal Preparing Aldehyde and Ketone ● Oxidation of primary alcohol ○ PCC with CH Cl 2 2 ● Oxidation of secondary alcohol ○ PCC with CH Cl 2 2 ○ Na C2 O2 w7th H SO 2 4 ● Ozonolysis of alkenes ○ 1) O 3with 2) DMS ● Acidcatalyzed hydration of terminal alkynes ○ H 2O ,4H O 2ith HgSO 4 ○ goes to more substituted ○ enol to keto ● Hydroborationoxidation of terminal alkynes ○ 1) R 2H with 2) H O 2 2aOH ○ goes to less substituted ● FriedelCrafts Acylation ○ ketone with a halide with Al(halide) 3 Introduction to Nucleophilic Addition Reaction ● Resonance A minor but significant positive charge (+1) on the carbonyl carbon. ● Inductive Carbonyl carbon has a partial positive charge because it is attached to an electronegative atom. ● Steric effect Ketone have two alkyl group which causes hindrance, but an aldehyde has one alkyl group which contribute less hindrance. Relative reactivity (most to least) 1. Formaldehyde 2. Aldehyde 3. Ketone The alkyl groups stabilize the carbonyl carbon. Alkyl and hydride group are not good leaving group. Nucleophilic addition under basic condition: If the nucleophile is strong and not a good leaving group, then the full addition would occur. Nucleophilic addition under acidic condition: Oxygen Nucleophile Hydrate Formation Carbonyl group can be converted into a hydrate. Steric effect: Electronic effect: Mechanism: Base: Acid: Acetal Formation: Mechanism: Cyclic Acetal: + This reaction is used for protection. This reaction can be reversed with: H O with [H ] 2 Examples: Stable Hemiacetal: Nitrogen Nucleophile: Primary amine: ● In acidic condition, the primary amine will give imine. ● Reagent: ○ Trace acid + ○ [H ] ○ TsOH Mechanism: This reaction is sensitive to pH. The pH needs to be around 45 because lower pH will protonate the amine causing it to not act as a nucleophile. Higher than around 5, the substance will not be protonated. Example: Secondary amine: ● Gives enamine ● Develop a double bond Mechanism: So, 1° Nitrogen loses a proton directly 2° Neighboring carbon loses the proton WolfKishner Reduction ● Reduction from carbonyl to alkane ● Hydrazine attack carbonyl to form hydrazone.
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