Lecture 7: Aromatic Aldehydes & Ketones PDF

Lecture 7 Aromatic Aldehydes & Ketones College of Pharmacy Department of Pharmaceutical Chemistry Sections -Introduction -Nomenclature -Synthesis -Reactions -Class activity -Re...

Lecture 7 Aromatic Aldehydes & Ketones College of Pharmacy Department of Pharmaceutical Chemistry Sections -Introduction -Nomenclature -Synthesis -Reactions -Class activity -References Intended Learning Outcomes (ILO’s) At the end of this unit students will be able to:  Know the structural differences between Aldehydes and Ketones.  know the common and IUPAC nomenclature of Aldehydes and Ketones.  Know how to synthesize an Aldehyde or a Ketone.  Know the different Nucleophilic reactions at the Carbonyl Carbon. 19-Dec-24 3 Aromatic aldehyde and ketones – Page - 15  Aromatic aldehyde and ketones are coming under the category of carbonyl compounds and can be described as molecules containing the carbonyl group, C=O. The carbonyl group of compounds are generally composed of Aldehydes, Ketones, Carboxylic acids, Esters, and Amides. 19-Dec-24 4 1) Nomenclature of Aldehydes and Ketones Page - 15  Aliphatic aldehydes are named in the IUPAC system by replacing the final –e of the name of the corresponding Alkane with -al.  Aldehydes in which –CHO group is attached to a ring system are named by adding the suffix carbaldehyde. 19-Dec-24 5  Aliphatic Ketones are named by replacing the final –e of the name of the corresponding Alkane with -one. The chain is then numbered in the way that gives the carbonyl carbon atom the lower possible number, and this number is used to designate its position. Propanone 2-Butanone 2-Pentanone (Acetone)  They can also be named by separately naming the two groups attached to the carbonyl group and adding the word ketone as a separate word. methyl propyl ketone methyl phenyl ketone diphenyl ketone (acetophenone) (benzophenone) 19-Dec-24 6 2) Synthesis of aldehydes and ketones from alcohols  Primary Alcohols on oxidation gives Aldehydes.  Secondary Alcohols on oxidation gives Ketones. 19-Dec-24 7 Reactions of aldehydes and ketones – Page-221 The most important reaction given by aldehydes and ketones are Nucleophilic addition reaction. A nucleophile, Nu-, is an electron rich species that will react with an electron poor species (here the C=O) Nucleophile addition reaction implies that two systems combine to a single entity. There are three fundamental events in a nucleophilic addition reaction: 1.formation of the new s bond between the nucleophile, Nu, to the electrophilic C of the C=O group 2.breaking of the p bond to the O resulting in the formation of an intermediate alkoxide 3.protonation of the intermediate alkoxide to give an alcohol derivative A) Nucleophilic addition: It is one of the most characteristic reaction of aldehydes and ketones where a nucleophile adds to the carbonyl group. General Reaction 19-Dec-24 8 Example of nucleophilic addition reaction 1) Addition of Hydrogen Cyanide (HCN) – Page-238 Note: Great care must be taken when working with HCN due to its high toxicity and volatility. Reactions involving HCN must be conducted in an efficient fume hood. 19-Dec-24 9 2. Addition of Organometallic compounds: Grignard reagents (RMgX) – Page-240  Grignard reagents react with formaldehyde to give a primary alcohol.  Grignard reagents react with all other aldehydes to give secondary alcohols.  Grignard reagents react with ketones s to give tertiary alcohols. 19-Dec-24 10 3. Addition of derivatives of Ammonia 19-Dec-24 11 4. Addition of Alcohols – Page-224 5. Addition of Hydride ion General reaction Specific Example 2-pentanone 2-pentanol NOTE: NaBH4 is a reducing agent and the conversion of ketone to alcohol is reduction. 19-Dec-24 12 B) Addition of Carbanions: -Page-372 1. The Knoevenagel condensation: Knoevenagel reaction is a modified aldol reaction, in which reaction of carbonyl compound with active Methylene compound, proceeds through Enolate formation, in presence of weakly basic conditions. Aldehyde Diethyl Malonate Mechanism: 19-Dec-24 13 2. Addition of Ylides: The Wittig reaction: General Reaction Specific example Cyclohexanone Phosphorus ylide Oxaphosphetane Methylenecyclohexane 19-Dec-24 14 C) Oxidation reactions: Aldehydes are oxidized to acids easily, whereas ketones are more resistant to oxidation, because ketones lack this hydrogen. General Reaction Aldehyde Acid Specific example 19-Dec-24 15 D) Haloform reaction: This reaction occurs in any aldehyde or ketone containing CH3CO- General Reaction Methyl ketone Carboxylate ion Iodoform Specific example Acetophenone 19-Dec-24 16 References Textbooks: Elements of organic chemistry” by H. Zimmerman and I. Zimmerman ISBN 0247960-9 Solomons, T.W. Graham “Organic Chemistry” 10th edition 2011; John Wiley & Sons. Online link & Video https://chem.libretexts.org https://www.khanacademy.org 19-Dec-24 17 Class activity-1 Q1) Write structural formulas for a) Cyclohexanecarbaldehyde b) 3 –methylcyclohexanecarbaldehyde c) 2,2-dibromocyclopentanecarbaldehyde Lets learn our nature and natural compounds containing Aldehydes and ketones 19-Dec-24 19