scoresvideos
Organic Chemistry
Table of Contents
Unit 19 Overview: Aldehydes & Ketones: Nucleophilic Addition
19.1 Naming Aldehydes and Ketones
19.2 Preparing Aldehydes and Ketones
19.3 Oxidation of Aldehydes and Ketones
19.4 Nucleophilic Addition Reactions of Aldehydes and Ketones
19.5 Nucleophilic Addition of H2O: Hydration
19.6 Nucleophilic Addition of HCN: Cyanohydrin Formation
19.7 Nucleophilic Addition of Hydride and Grignard Reagents: Alcohol Formation
19.8 Nucleophilic Addition of Amines: Imine and Enamine Formation
19.9 Nucleophilic Addition of Hydrazine: The Wolff–Kishner Reaction
19.10 Nucleophilic Addition of Alcohols: Acetal Formation
19.11 Nucleophilic Addition of Phosphorus Ylides: The Wittig Reaction
19.12 Biological Reductions
19.13 Conjugate Nucleophilic Addition to α,β‑Unsaturated Aldehydes and Ketones
19.14 Spectroscopy of Aldehydes and Ketones

Aldehydes and ketones are organic compounds with a carbonyl group. They're named using IUPAC rules, with aldehydes ending in "-al" and ketones in "-one". Understanding their naming conventions is crucial for identifying their structures and properties.

These compounds play vital roles in various industries and biological processes. Mastering their nomenclature is essential for communicating about them effectively in chemistry and related fields. Let's dive into the specifics of naming these important molecules.

Nomenclature of Aldehydes and Ketones

Systematic Naming and IUPAC Nomenclature

  • Aldehydes and ketones are named using systematic naming conventions established by IUPAC (International Union of Pure and Applied Chemistry)
  • IUPAC nomenclature provides a standardized method for naming organic compounds, including those with carbonyl functional groups
  • Common names are still used for some simple aldehydes and ketones, but systematic names are preferred in scientific literature

IUPAC nomenclature for aldehydes and ketones

  • Aldehydes
    • Characterized by the presence of a formyl group (-CHO) attached to the end of a carbon chain
    • Named by replacing the -e ending of the corresponding alkane with -al (propanal, hexanal)
    • Aldehyde carbon always designated as C1, with numbering starting from this carbon
    • No need to specify position of the aldehyde group as it is always at the end of the chain
    • Substituents on the carbon chain are numbered and named as usual (2-methylbutanal, 3-ethylhexanal)
  • Ketones
    • Characterized by the presence of a carbonyl group (-CO-) within a carbon chain
    • Named by replacing the -e ending of the corresponding alkane with -one (propanone, hexanone)
    • Position of the ketone group is indicated by a number followed by a dash before the name (2-pentanone, 3-heptanone)
    • Numbering starts from the end of the chain that gives the ketone the lowest possible number
    • Substituents on the carbon chain are numbered and named as usual (3-methyl-2-butanone, 4-ethyl-3-hexanone)

Common names of simple carbonyls

  • Formaldehyde (methanal): HCHO, the simplest aldehyde
  • Acetaldehyde (ethanal): CH3CHO, a common solvent and precursor to acetic acid
  • Acetone (propanone): CH3COCH3, a widely used solvent and nail polish remover
  • Benzaldehyde: C6H5CHO, a fragrant compound with an almond-like odor
  • Butyraldehyde (butanal): CH3CH2CH2CHO, used in the synthesis of rubber accelerators and plasticizers
  • Cyclopentanone: a cyclic ketone with a five-membered ring, used in the production of pharmaceuticals and fragrances

Structures from carbonyl names

  • Aldehydes
    1. Determine the number of carbons in the main chain from the root name (heptanal = 7 carbons)
    2. Draw a straight chain of the appropriate number of carbons
    3. Attach the aldehyde group (-CHO) to one end of the chain
    4. Add any substituents at the specified positions (4-methylhexanal: CH3CH(CH3)CH2CH2CHO)
    5. Fill in the remaining hydrogen atoms to complete the structure
  • Ketones
    1. Identify the number of carbons in the main chain from the root name (4-heptanone = 7 carbons)
    2. Draw a straight chain of the appropriate number of carbons
    3. Locate the position of the ketone group (-CO-) based on the number in the name (4-heptanone: CH3CH2CH2COCH2CH2CH3)
    4. Add any substituents at the specified positions (3-methyl-2-pentanone: CH3C(CH3)COCH2CH3)
    5. Fill in the remaining hydrogen atoms to complete the structure
    • The carbonyl group (C=O) is the functional group that defines aldehydes and ketones

Key Terms to Review (39)

Betaine: Betaine is an organic compound with a quaternary ammonium and a carboxylate group that acts as a methyl donor in various biological reactions, including methylation processes. It is not directly involved in the Wittig reaction but is relevant in organic chemistry for its role in transferring methyl groups.
Formyl: In organic chemistry, formyl refers to a functional group with the structure R-CHO, where R can be hydrogen or an organic substituent, and CHO denotes a carbonyl group bonded to a hydrogen. It is characteristic of aldehydes, distinguishing them from ketones which have two organic groups attached to the carbonyl carbon.
Acyl (a-sil) group: An acyl group is a functional group derived from carboxylic acids by removing a hydroxyl group (-OH), typically represented as RCO-, where R is an organic substituent. In the context of naming aldehydes and ketones, it indicates the presence of a carbonyl group (C=O) bonded to an alkyl or aryl group.
Symmetry-allowed, symmetry-disallowed: In the context of organic chemistry, a symmetry-allowed reaction occurs when the molecular orbitals of reacting molecules align in such a way that allows for electron sharing or transfer, facilitating the reaction. These reactions comply with the symmetry rules governing conjugated pi systems, enabling smooth transition states.
Cannizzaro reaction: The Cannizzaro reaction is a chemical reaction where an aldehyde is simultaneously reduced and oxidized in the presence of a strong base, leading to the formation of a primary alcohol and a carboxylate salt. This reaction involves no external reducing agent, as one aldehyde molecule acts as the oxidant and another as the reductant.
β Diketone: A β-diketone is an organic compound containing two ketone groups separated by a carbon atom, which is the beta (β) position relative to each ketone group. These molecules are characterized by the presence of hydrogen atoms on the carbon between the two carbonyl (C=O) groups, making them acidic and prone to enolate ion formation.
Phosphorane: Phosphorane is a pentavalent phosphorus compound with four substituents and one negative charge, commonly involved in the Wittig reaction to create alkenes from aldehydes or ketones. It acts as a nucleophile, attacking the carbonyl carbon of an aldehyde or ketone to form a double bond.
IUPAC system of nomenclature: The IUPAC system of nomenclature is a standardized method for naming organic compounds devised by the International Union of Pure and Applied Chemistry. It ensures clarity and uniformity in the naming process, allowing chemists worldwide to understand precisely which compound is being referred to.
Wittig reaction: The Wittig reaction is a chemical process used in organic chemistry to synthesize alkenes from aldehydes or ketones by reacting them with phosphorus ylides. This reaction proceeds through the nucleophilic addition of a phosphorus ylide to the carbonyl group, followed by elimination to form the alkene.
Functional group: A functional group is a specific group of atoms within a molecule that determines the chemical behavior and reactions of that molecule. It is essentially the reactive part of a molecule that gives it its unique properties in organic chemistry.
Ketals: Ketals are a class of organic compounds formed by the reaction of ketones with alcohols in the presence of an acid catalyst. They consist of a central carbon atom bonded to two alkyl or aryl groups and two ether-like oxygen atoms.
Acetals, R2C(OR′)2: Acetals are chemical compounds characterized by two ether-like OR′ groups attached to the same carbon atom, which is also connected to two other R groups. They are formed from the reaction of aldehydes or ketones with alcohols under acidic conditions.
Acetyl group: An acetyl group is a functional group in organic chemistry consisting of a methyl group single-bonded to a carbonyl. The formula is represented as CH3CO-.
Formaldehyde: Formaldehyde is a simple aldehyde compound with the chemical formula CH2O. It is a colorless, flammable gas with a pungent odor that is widely used in various industrial and commercial applications. Formaldehyde is a key term that is important in the context of several organic chemistry topics, including functional groups, oxidation of alkenes, naming aldehydes and ketones, nucleophilic addition of water, and spectroscopy of aldehydes and ketones.
Nomenclature: Nomenclature refers to the systematic naming and classification of chemical compounds based on established rules and conventions. It is a crucial aspect of organic chemistry, as it provides a standardized way to identify and communicate the structures of various compounds.
Acetaldehyde: Acetaldehyde is a colorless, flammable organic compound with the chemical formula CH3CHO. It is the simplest aliphatic aldehyde and is an important intermediate in various chemical processes and metabolic pathways.
-al: The suffix '-al' is used to indicate the presence of an aldehyde functional group, which is a carbonyl group (C=O) bonded to a hydrogen atom. This term is particularly relevant in the context of organic chemistry, specifically in the topics of functional groups and the naming of aldehydes and ketones.
-one: The suffix '-one' is used in organic chemistry to indicate the presence of a carbonyl group, which is a carbon-oxygen double bond. This functional group is found in two important classes of organic compounds: aldehydes and ketones. The '-one' suffix helps to identify the location and nature of the carbonyl group within the molecule.
Benzaldehyde: Benzaldehyde is an aromatic aldehyde compound with the chemical formula C6H5CHO. It is a colorless liquid with a characteristic almond-like odor and is widely used in the production of various organic compounds, including pharmaceuticals, flavors, and fragrances.
IUPAC: IUPAC, or the International Union of Pure and Applied Chemistry, is the authoritative body responsible for establishing standardized rules and guidelines for the naming and representation of chemical compounds. This term is crucial in the context of organic chemistry, as it provides a systematic and unambiguous way to name and identify various classes of organic molecules.
Aldehyde: An aldehyde is a class of organic compounds containing a carbonyl group (C=O) where the carbon atom is bonded to one hydrogen atom and one alkyl or aryl group. Aldehydes are important functional groups in organic chemistry and are involved in various reactions and synthesis pathways.
Acetone: Acetone is a simple organic compound with the chemical formula CH3COCH3. It is a colorless, volatile, flammable liquid that is widely used as a solvent and in various chemical processes. Acetone is a key term that is relevant in the context of several important organic chemistry topics.
Ketone: A ketone is a functional group in organic chemistry that consists of a carbonyl group (a carbon-oxygen double bond) bonded to two alkyl or aryl groups. Ketones are widely encountered in various organic chemistry topics, including the hydration of alkynes, oxidative cleavage of alkynes, organic synthesis, oxidation and reduction reactions, and the chemistry of aldehydes and ketones.
Functional Group: A functional group is a specific arrangement of atoms within an organic molecule that determines its chemical reactivity and properties. These groups are the key structural features that define the behavior and classification of organic compounds.
Propanal: Propanal is the simplest aliphatic aldehyde, with the molecular formula C$_{3}$H$_{6}$O. It is a colorless, volatile liquid with a pungent, fruity odor. Propanal is an important organic compound that is closely related to the topics of naming aldehydes and ketones, nucleophilic addition reactions, spectroscopy, and carbonyl condensation reactions.
Methanal: Methanal, also known as formaldehyde, is the simplest aldehyde compound with the chemical formula CH2O. It is a colorless, flammable gas with a characteristic pungent odor, and it plays a crucial role in the context of naming aldehydes and ketones.
Hexanal: Hexanal is an aldehyde compound with the chemical formula C$_6$H$_{12}$O. It is a volatile, colorless liquid that is commonly used as a flavoring agent and in the production of various chemicals.
2-pentanone: 2-pentanone is a simple ketone compound with the chemical formula CH3C(O)CH2CH3. It is a colorless, volatile liquid with a sweet, fruity odor and is commonly used as a solvent and in the production of other chemicals.
Propanone: Propanone, also known as acetone, is a simple ketone compound with the chemical formula CH$_3$COCH$_3$. It is a colorless, volatile, and flammable liquid that is widely used in various industrial and commercial applications. Propanone is particularly relevant in the context of the topics 19.1 Naming Aldehydes and Ketones and 19.7 Nucleophilic Addition of Hydride and Grignard Reagents: Alcohol Formation.
Hexanone: Hexanone is a simple aliphatic ketone with the molecular formula C6H12O. It is a colorless, flammable liquid with a characteristic odor, and is commonly used as a solvent and an intermediate in organic synthesis.
Formyl Group: The formyl group is a functional group in organic chemistry that consists of a carbonyl group (a carbon-oxygen double bond) attached to a hydrogen atom. It is represented by the chemical formula -CHO and is the simplest aldehyde functional group.
3-heptanone: 3-heptanone is a ketone compound with the molecular formula C$_{7}$H$_{14}$O. It is a colorless liquid with a sweet, fruity odor and is commonly used as a solvent and in the production of other chemical compounds.
Systematic Naming: Systematic naming is a standardized method for assigning unique and unambiguous names to organic compounds based on their chemical structure. It provides a clear and logical system for identifying and communicating the identity of these compounds.
Common Names: Common names, also known as trivial names or popular names, are informal designations used to identify chemical compounds that are more easily recognizable than their formal systematic names. These simplified names are widely used in everyday conversations and literature, providing a more accessible way to refer to various organic compounds, including aldehydes, ketones, carboxylic acids, nitriles, and amines.
Ethanal: Ethanal, also known as acetaldehyde, is the simplest aliphatic aldehyde with the chemical formula CH3CHO. It is a volatile, colorless liquid with a pungent, fruity odor. Ethanal is an important intermediate in organic chemistry, particularly in the context of naming aldehydes and ketones, nucleophilic addition reactions, and spectroscopic analysis.
Cyclopentanone: Cyclopentanone is a cyclic ketone compound with a five-membered carbon ring structure. It is an important organic compound that plays a key role in various reactions and synthetic processes discussed in the context of the specified topics.
Butyraldehyde: Butyraldehyde is an aldehyde with the chemical formula CH3CH2CH2CHO. It is a colorless, flammable liquid with a pungent odor, and is used as an industrial solvent and in the production of other chemicals.
Butanal: Butanal is an aldehyde compound with the chemical formula CH3CH2CH2CHO. It is a colorless, flammable liquid with a pungent, fruity odor. Butanal is an important organic compound that is relevant in the context of naming aldehydes and ketones, spectroscopy of aldehydes and ketones, and carbonyl condensations, specifically the aldol reaction.
Carbonyl group: A carbonyl group is a functional group characterized by a carbon atom double-bonded to an oxygen atom, represented as C=O. This group is pivotal in organic chemistry as it forms the backbone of various important classes of compounds, influencing their chemical properties and reactivity.