Aldehydes and Ketones Notes PDF

ALDEHYDES AND KETONES CARBONYL COMPOUNDS CARBONYL COMPOUNDS Some Common Classes Carbonyl Compounds  ALDEHYDES AND KETONES Aldehydes and ketones are organic compounds which incorporate a carbonyl functional group, C=O. The carbon atom of this group has two remaining bonds that may be occupied...

ALDEHYDES AND KETONES CARBONYL COMPOUNDS CARBONYL COMPOUNDS Some Common Classes Carbonyl Compounds  ALDEHYDES AND KETONES Aldehydes and ketones are organic compounds which incorporate a carbonyl functional group, C=O. The carbon atom of this group has two remaining bonds that may be occupied by hydrogen or alkyl or aryl substituents. If at least one of these substituents is hydrogen, the compound is an aldehyde RCHO or RCH=O. If neither is hydrogen, the compound is a ketone RCOR` (R and R`=alkyl or aryl). ALDEHYDES  COMMON NAMES OF ALDEHYDES In the common system, aldehydes are named from the common names of the corresponding carboxylic acid. The ‘oic acid’ ending is replaced with ‘aldehyde’. The aldehyde group is always at the end of a chain (terminal).  COMMON NAMES OF ALDEHYDES Substituents locations are given using Greek letters (α, β, γ, δ, ε, ω.) beginning with the carbon next to the carbonyl carbon, the α-carbon. β-bromobutyraldehyde γ-hydroxyvaleraldehyde α-phenylacetaldehyde  COMMON NAMES OF ALDEHYDES Aromatic aldehydes are usually designated as derivatives of the simplest aromatic aldehyde, Benzaldehyde Benzaldehyde p-Nitrobenzaldehyde o-Hydroxybenzaldehyde p-Methoxybenzaldehyde Salicylaldehyde Anisaldehyde  IUPAC Nomenclature of Aldehydes Select the longest continuous carbon chain that contains the C=O group and replace the ending -e by the suffix -al The CHO group is assigned the number “1” position and takes precedence over other functional groups that may the present such as –OH, C=C …… If the CHO group is bonded to a ring, name the ring and add the suffix -carbaldehyde. IUPAC Nomenclature of Aldehydes Nomenclature of Aldehydes IUPAC Nomenclature of Aldehydes SEATWORK  SEATWORK 2-chloro-pentanal cyclohexanecarbaldehyde 3-bromo-2-methylpropanal 5-chloro-2-methylcyclohexanecarbaldehyde KETONES  IUPAC Nomenclature of Ketones ❖ Common name: ❑ listing the alkyl substituents attached to the carbonyl group alphabetically, followed by the word ketone. As with aldehydes, substituents locations are given in common names using Greek letters (α, β, γ, δ, ε, ω.) beginning with the α-carbon. Propanone Phenyl ethanone 3-Buten-2-one Diphenylmethanone  IUPAC Nomenclature of Ketones ❖IUPAC system: Find the longest chain containing the carbonyl group, and change the -e ending of the parent alkane to the suffix -one. Number the carbon chain to give the carbonyl carbon the lower number. Apply all of the other usual rules of nomenclature. Ketones are just below aldehydes in nomenclature priority. A ketone group is named as an ‘oxo’ substituent in an aldehyde. IUPAC Nomenclature of Ketones Seatwork Seatwork 2-pentanone 3-methyl-2-butanone 3-hexanone cyclopentanone 2-bromocyclopentanone 2-bromo-5-methylcyclohexanone Preparation of Aldehydes Preparation of Ketones R  Preparation of Ketones Hydration of Alkynes Example:  Preparation of Ketones Friedel-Crafts Acylation Example: Preparation of Aldehydes and Ketones Ozonolysis of alkenes SEATWORK SEATWORK  Reactions of Aldehydes Oxidation Aldehydes are oxidized to carboxylic acids by a variety of oxidizing agents, including potassium dichromate.  Reactions of Aldehydes and Ketones Ketones, in contrast, resist oxidation by most oxidizing agents, including potassium dichromate and molecular oxygen. To determine if a compound is an aldehyde or ketone, we can treat the compound with a mild oxidizing agent. If it can be oxidized, it is an aldehyde; otherwise, it is a ketone. One reagent that has been used for this purpose is Tollens’ reagent. Tollens’ reagent is prepared from silver nitrate and ammonia in water. If this reaction is carried out properly, the silver metal precipitates as a smooth, mirror-like deposit on the inner surface of the reaction vessel, leading to the name silver-mirror test.  Reactions of Aldehydes and Ketones Reduction Aldehydes are reduced to primary alcohols and ketones are reduced to secondary alcohols.  Reactions of Aldehydes and Ketones Reduction The reagent most commonly used in the laboratory for the reduction of an aldehyde or a ketone is sodium borohydride, NaBH4.  Reactions of Aldehydes and Ketones Reduction REACTIONS OF ALDEHYDES AND KETONES 1) LiAlH4 / dry ether or NaBH4 2) H3O+ 1) LiAlH4 / dry ether or NaBH4 2) H3O+ 1) LiAlH4 / dry ether or NaBH4 2) H3O+  Reactions of Aldehydes and Ketones Addition of Alcohols Hemiacetal (new) Acetal (new)  Reactions of Aldehydes and Ketones Keto-Enol Tautomerism  Reactions of Aldehydes and Ketones Keto-Enol Tautomerism  Reactions of Aldehydes and Ketones Keto-Enol Tautomerism  Reactions of Aldehydes and Ketones Keto-Enol Tautomerism Seatwork Seatwork