Aldehydes And Ketones
Carbonyl goup: the oxygen atom is electronegative Aldehydes and Ketones are molecules of carbon, oxygen and hydrogen that have, as part of their structure a reactive group called a carbonyl group, typically written C=O. The carbon atom in a carbonyl group can still form two additional covalent bonds. If this carbon atoms is joined with two other carbon atoms then the compound formed is a ketone, but if this carbon is joined with a hydrogen, then the compound is an aldehyde. The oxygen atom in the carbonyl group pulls the shared electrons towards it, causing an imbalance in the distribution of positive and negative charges. (The oxygen is said to be more electronegative). This polarity of charge has two effects on the physical properties of molecules containing this reactive group; aldehydes and ketones have higher boiling points, and they are more water soluble than similar hydrocarbons. The unequal charges on the oxygen atom and the carbon atom of the carbonyl group also affects the kind and type of chemical reactions that these molecules undergo. For example, water will interact with the carbonyl group very, very rapidly forming a short lived intermediate with two -OH (hydroxyl groups) which then very rapidly breaks up into water and a carbonyl group once more. The rapid addition of water (H-OH) to the carbonyl group produces a hydrate which is very unstable and cannot be isolated as a separate molecule or compound. However, if, instead of water, an alcohol (R-OH) is used a similar kind of chemical reaction takes place in which a hemiacetal is formed. Most of these hemiacetals are not stable and quickly break down once more, however, there is at least one example where a molecule with five carbon atoms in a chain with an -OH group at one end, and an aldehyde group (-H Continue reading >>
Lab Report-determining Reactions Of Aldehydes And Ketones
Abstract The aim of this experiment was to identify which functional groups the various chemicals and unknown substances belonged to using the different reaction tests. The main purpose was to determine the reactions of Aldehydes and Ketones. Aldehydes and Ketones are organic compounds consisting of the carbonyl functional group. Aldehydes contain their carbonyl group at the end of the carbon chain and are susceptible to oxidation while Ketones contain theirs in the middle of the carbon chain and are resistant to oxidation. Jones’s Test, Tollen’s Reagent and Iodoform Reaction were the three tests used to determine the reactions of aldehydes and ketones. The Chromic Anhydride test caused Aldehydes to turn blue, and Ketones orange. The Tollen’s Reagent test caused the oxidation of aldehydes thus forming a mirror-like image in the test tube rendering it a positive test and the Iodoform reaction produced a yellow precipitate in the test tube which concluded the presence of an aldehyde. Introduction The carbon-oxygen double bond is one of the most important functional groups, due to its ubiquity, which are involved in most important biochemistry processes. Reactivity of this group is ruled by the electron imbalance in the πorbitals of the bond between a more electronegative and a carbon atom. This carbon atom is more likely to undergo a nucleophillic attack, especially if the oxygen is protonated. If the carbonyl group has hydrogen’s in the α-position, it can tautomerise to the enol, thus, Keto tautomer can become Enol tautomer. Aldehydes and Ketones are organic compounds that consist of the carbonyl functional group, C=O. The carbonyl group that consists of one alkyl substituent and one hydrogen is the Aldehyde and those containing two alkyl substituents are calle Continue reading >>
Journal Of The Chemical Society (resumed)
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Aldehydes & Ketones
Melanin - a polymeric substance involving many interconnected cyclic ketone units that colors human hair & skin Functional Group Aldehydes Carbonyl (-C=O) at end of chain Contains a polar bond RCHO Aliphatic chains NOT as part of ... Aliphatic rings or Aromatic rings Ketones Carbonyl (-C=O) in middle of chain Contains a polar bond RCOR Aliphatic chains Aliphatic rings NOT as part of Aromatic rings Nomenclature Aldehydes IUPAC Alkanal Carbonyl C = #1 Common Prefixaldehyde Ketones IUPAC Alkanone Propanone = acetone Carbonyl C = lowest # possible Common Alkyl alkyl ketone Multi-functional Group Compounds What name do you use when there is more than one functional group? To determine which suffix to use, follow this priority list (high to low): Substituent name Aldehyde Ketone oxo- Alcohol hydroxy- Alkene en- (before suffix) Alkyne yn- (before suffix) Alkoxy (ether) alkoxy- Alkyl alkyl- Halogen halo- Isomerism Aldehydes Constitutional Skeletal Functional group (this is the second time we encounter this type of isomerism) Ketones Constitutional Skeletal Positional Functional group Common & Naturally Occurring Aldehydes & Ketones Aldehydes Formaldehyde methanal Acetaldehyde ethanal Odors/Flavors Vanillin Benzaldehyde --> Cinnamaldehyde Lots of nuts & spices Ketones Acetone propanone Odors/Flavors Cloves (2-heptanone) Lots of nuts & spices Butter (butanedione) Fresh-mown hay (coumarin) Steroid Hormones Testosterone Progesterone Cortisone Physical Properties Aldehydes Boiling Point AlkanesRCOOH + Ag(s) Ketones RCOR + Ag+ --> NR (c) The inside of the beaker becomes coated with metallic silver. (b) The solution darkens as ethanal is oxidized to ethanoic acid. (a) An aqueous solution of ethanal is added to a solution of silver nitrate. Chemical Reactions - Fehling’s or Bene Continue reading >>
Sustainable Synthesis Of Aldehydes, Ketones Or Acids From Neat Alcohols Using Nitrogen Dioxide Gas, And Related Reactions.
Abstract Benzylic alcohols are quantitatively oxidized by gaseous nitrogen dioxide to give pure aromatic aldehydes. The reaction gas mixtures are transformed to nitric acid, which renders the processes free of waste. The exothermic gas-liquid or gas-solid reactions profit from the solubility of nitrogen dioxide in the neat benzylic alcohols. The acid formed impedes further oxidation of the benzaldehydes. The neat isolated benzaldehydes and nitrogen dioxide quantitatively give the benzoic acids. Solid long-chain primary alcohols are directly and quantitatively oxidized with nitrogen dioxide gas to give the fatty acids in the solid state. The oxidations with ubiquitous nitrogen dioxide are extended to solid heterocyclic thioamides, which gives disulfides, and to diphenylamine, which gives tetraphenylhydrazine. These sustainable (green) specific oxidation procedures produce no dangerous residues from the oxidizing agent or from auxiliaries. Continue reading >>
Aldehydes And Ketones
Introduction We will focus more specifically on the organic compounds that incorporate carbonyl groups: aldehydes and ketones. Key Terms Aldehyde Formyl group Ketone Hydrogen bonding Hydration Hydrate Objectives Identify IUPAC names for simple aldehydes and ketones Describe the boiling point and solubility characteristics of aldehydes and ketones relative to those of alkanes and alcohols Characterize the process of nucleophilic addition to the carbonyl group The carbonyl group is shown below in the context of synthesizing alcohols. This functional group is the key component of aldehydes and ketones, which we will discuss here. Nomenclature for Aldehydes and Ketones Aldehydes and ketones are structurally similar; the only difference is that for an aldehyde, the carbonyl group has at most one substituent alkyl group, whereas the carbonyl group in a ketone has two. Several examples of aldehydes and ketones are depicted below. Aldehydes are named by replacing the -e ending of an alkane with -al (similarly to the use of -ol in alcohols). The base molecule is the longest carbon chain ending with the carbonyl group. Furthermore, the carbon atom in the carbonyl group is assumed to be carbon 1, so a number is not needed in the IUPAC name to identify the location of the doubly bonded oxygen atom. If the chain contains two carbonyl groups, one at each end, the correct suffix is -dial (used in the same manner as -diol for compounds with two hydroxyl groups). An example aldehyde is shown below with its IUPAC name. One- and two-carbon aldehydes have common names (one of which you will likely be familiar with) in addition to their systematic names. Both names are acceptable. Sometimes, the carbonyl group plus one proton (called a formyl group) must be treated separately for nomenclatu Continue reading >>
Electronic Structures Of Molecules X. Aldehydes, Ketones And Related Molecules
Electron configurations for the normal states of H2CO, CH3HCO, Cl2CO are explicitly given, also for the low excited states of H2CO. The structures, ionization potentials, and longest wavelength electronic band spectra of these and other related or analogous molecules (saturated aldehydes, ketones, thioaldehydes, thioketones, etc.) are interpreted in relation to these configurations. In particular is it shown that the minimum ionization potential of or corresponds to removal of a nonbonding 2p electron from the O atom or a nonbonding 3p from the S atom, unless the groups attached to the C contain other unusually easily ionized electrons. Similarly, the longest wavelength band system, commonly attributed to the C=O (or C=S) double bond, corresponds to excitation of the nonbonding 2po or 3ps to an excited orbital which is largely but probably not quite wholly localized in the C=O or C=S bond, and which has C↔O or C↔S antibonding power, i.e., loosens the bond somewhat. This excitation process is responsible for color in the compounds. The C=O (or C=S) bond is a true double bond in the sense that the binding is effected essentially by two pairs of C–O (or C–S) bonding electrons. The C=O bond is essentially the same also in saturated monobasic acids RCOOH or at least in their esters. Continue reading >>
Carbonyl Group
Carbonyl group, in organic chemistry, a divalent chemical unit consisting of a carbon (C) and an oxygen (O) atom connected by a double bond. The group is a constituent of carboxylic acids, esters, anhydrides, acyl halides, amides, and quinones, and it is the characteristic functional group (reactive group) of aldehydes and ketones. Carboxylic acids (and their derivatives), aldehydes, ketones, and quinones are also known collectively as carbonyl compounds. Because of a difference in the electron affinities of the carbon and oxygen atoms, the electron pairs that constitute the double bond are held closer to the oxygen atom than to the carbon atom; the electron-rich oxygen atom acquires a negative charge and the electron-deficient carbon atom a positive charge. Thus, molecules containing the carbonyl group are polar. Compounds containing a carbonyl group have higher melting and boiling points than hydrocarbons containing the same number of carbon atoms and are more soluble in polar solvents such as water. The carbonyl group can enter into a variety of chemical reactions; nucleophilic reagents (electron-rich reagents) are attracted to the carbon atom, whereas electrophilic reagents (electron-seeking reagents) are attracted to the oxygen atom. Aldehydes and ketones contain carbonyl groups attached to alkyl or aryl groups and a hydrogen atom or both. These groups have little effect on the electron distribution in the carbonyl group; thus, the properties of aldehydes and ketones are determined by the behaviour of the carbonyl group. In carboxylic acids and their derivatives, the carbonyl group is attached to one of the halogen atoms or to groups containing atoms such as oxygen, nitrogen, or sulfur. These atoms do affect the carbonyl group, forming a new functional group with d Continue reading >>
9. Aldehydes, Ketones, And Related Compounds
Aldehydes and ketones originate as fermentation metabolites as well as oxidation products and in many situations the source is difficult to discern. Grape-derived aldehydes are also detectable in juice following crushing, and particularly six-carbon aldehydes formed by enzymatic oxidation of grape lipids. Short branched-chain aldehydes, including 2-methylpropanal and 2- and 3-methylbutanal, are associated with dried fruit, sweet and fusel type aromas. Methional and phenylacetaldehyde are very potent aldehydes arising from the oxidation of corresponding alcohols, which are derived from amino acids methionine and phenylalanine, respectively. A significant number of carbonyls originate from oxidation of complex precursor molecules such as organic acids, which result in highly functionalized products. Carbonyl compounds also react reversibly with other wine nucleophiles, including bisulfite, the phloroglucinol ring of flavonoids, and thiols. Any analysis of aldehydes or ketones should account for the possibility of these various addition products, releasing the carbonyls in the course of the analysis. Continue reading >>
21.10: Aldehydes And Ketones
Identify the general structure for an aldehyde and a ketone. Use common names to name aldehydes and ketones. Use the IUPAC system to name aldehydes and ketones. The next functional group we consider, the carbonyl group, has a carbon-to-oxygen double bond. Carbonyl groups define two related families of organic compounds: the aldehydes and the ketones. The carbonyl group is ubiquitous in biological compounds. It is found in carbohydrates, fats, proteins, nucleic acids, hormones, and vitamins—organic compounds critical to living systems. In a ketone, two carbon groups are attached to the carbonyl carbon atom. The following general formulas, in which R represents an alkyl group and Ar stands for an aryl group, represent ketones. In an aldehyde, at least one of the attached groups must be a hydrogen atom. The following compounds are aldehydes: In condensed formulas, we use CHO to identify an aldehyde rather than COH, which might be confused with an alcohol. This follows the general rule that in condensed structural formulas H comes after the atom it is attached to (usually C, N, or O). The carbon-to-oxygen double bond is not shown but understood to be present. Because they contain the same functional group, aldehydes and ketones share many common properties, but they still differ enough to warrant their classification into two families. Here are some simple IUPAC rules for naming aldehydes and ketones: The stem names of aldehydes and ketones are derived from those of the parent alkanes, defined by the longest continuous chain (LCC) of carbon atoms that contains the functional group. For an aldehyde, drop the -e from the alkane name and add the ending -al. Methanal is the IUPAC name for formaldehyde, and ethanal is the name for acetaldehyde. For a ketone, drop the -e from t Continue reading >>
How Are Aldehydes And Ketones Alike?
Both aldehydes (R-CHO) and ketones (R-CO-R') are called carbonyl compounds as they have the electron-withdrawing carbonyl group (C=O) in their molecules. On reduction both these classes of compounds yield respective alcohols. Aldehydes are converted to primary alcohols, and ketones to secondary alcohols. Both aldehydes and ketones undergo addition reactions at the CO group with compounds such as NH3, NH2OH, HCN and NaHSO3. On treatment with PCl5, the oxygen atom of the CO group gets replaced by chlorine, and they form dichloro compounds of the types R-CHCl2 and R-CCl2-R' respectively. Both undergo self-condensation in the presence of alkalis. Both acetaldehyde and acetone (and other methyl ketones) form iodoform with iodine and alkali. Aldehydes on oxidation are converted to carboxylic acids with same number of carbon atoms. Though ketones resist oxidation, they can be oxidised by strong oxidising agents like chromic acid to carboxylic acids containing lesser number of carbon atoms, as the molecule gets ruptured at the CO group. One major difference between aldehydes and ketones is that the former have distinct reducing properties. Aldehydes reduce Tollen's reagent to metallic silver, and Fehling's solution to red cuprous oxide. Continue reading >>
Aldehydes, Ketones, Carboxylic Acids, And Esters
By the end of this section, you will be able to: Describe the structure and properties of aldehydes, ketones, carboxylic acids and esters Another class of organic molecules contains a carbon atom connected to an oxygen atom by a double bond, commonly called a carbonyl group. The trigonal planar carbon in the carbonyl group can attach to two other substituents leading to several subfamilies (aldehydes, ketones, carboxylic acids and esters) described in this section. Aldehydes and Ketones Both aldehydes and ketones contain a carbonyl group, a functional group with a carbon-oxygen double bond. The names for aldehyde and ketone compounds are derived using similar nomenclature rules as for alkanes and alcohols, and include the class-identifying suffixes –al and –one, respectively: In an aldehyde, the carbonyl group is bonded to at least one hydrogen atom. In a ketone, the carbonyl group is bonded to two carbon atoms: In both aldehydes and ketones, the geometry around the carbon atom in the carbonyl group is trigonal planar; the carbon atom exhibits sp2 hybridization. Two of the sp2 orbitals on the carbon atom in the carbonyl group are used to form σ bonds to the other carbon or hydrogen atoms in a molecule. The remaining sp2 hybrid orbital forms a σ bond to the oxygen atom. The unhybridized p orbital on the carbon atom in the carbonyl group overlaps a p orbital on the oxygen atom to form the π bond in the double bond. Like the C=O bond in carbon dioxide, the C=O bond of a carbonyl group is polar (recall that oxygen is significantly more electronegative than carbon, and the shared electrons are pulled toward the oxygen atom and away from the carbon atom). Many of the reactions of aldehydes and ketones start with the reaction between a Lewis base and the carbon atom at Continue reading >>
14.9 Aldehydes And Ketones: Structure And Names
Learning Objectives Identify the general structure for an aldehyde and a ketone. Use common names to name aldehydes and ketones. Use the IUPAC system to name aldehydes and ketones. The next functional group we consider, the carbonyl group, has a carbon-to-oxygen double bond. Carbonyl groups define two related families of organic compounds: the aldehydes and the ketones. Note The carbonyl group is ubiquitous in biological compounds. It is found in carbohydrates, fats, proteins, nucleic acids, hormones, and vitamins—organic compounds critical to living systems. In a ketone, two carbon groups are attached to the carbonyl carbon atom. The following general formulas, in which R represents an alkyl group and Ar stands for an aryl group, represent ketones. In an aldehyde, at least one of the attached groups must be a hydrogen atom. The following compounds are aldehydes: In condensed formulas, we use CHO to identify an aldehyde rather than COH, which might be confused with an alcohol. This follows the general rule that in condensed structural formulas H comes after the atom it is attached to (usually C, N, or O). The carbon-to-oxygen double bond is not shown but understood to be present. Because they contain the same functional group, aldehydes and ketones share many common properties, but they still differ enough to warrant their classification into two families. Continue reading >>
Chapter 13 – Hydroxy-aldehydes And -ketones And Related Compounds: Dicarbonyl Compounds
Publisher Summary This chapter describes the methods of preparation and reactions of hydroxy-aldehydes and -ketones; sulfur and nitrogen analogues of hydroxy-aldehydes and –ketones; and dicarbonyl compounds. The photochemical decomposition of alkyl nitrites and related compounds leading to the formation of hydroxy-oximes, the Barton reaction, which is used extensively for introducing keto groups into classically unreactive positions in steroids and terpenes, is discussed. Butadiene is converted into dialdehydes by reaction with carbon monoxide in the presence of diruthenium trioxide and tributylphosphine. Adipaldehyde is prepared by the ozonization of cyclohexene with oxygen-free ozone, followed by hydrogenation of the ozonide in the presence of palladium–charcoal in 68% yield. α-Diketones are synthesized from ethyl acetoacetate and aldehydes. One-electron reduction of biacetyl or the one-electron oxidation of acetoin leads to the formation of the same semidone radical, which can be detected by electron spin resonance. Light-induced addition reactions of β-diketones to alkenes result in the formation of δ-diketones. Nitration of metal chelates of acetonylacetone is achieved using copper(II) nitrate and acetic anhydride. Copyright © 1975 Elsevier B.V. All rights reserved. Continue reading >>
Ketone
Not to be confused with ketone bodies. Ketone group Acetone In chemistry, a ketone (alkanone) /ˈkiːtoʊn/ is an organic compound with the structure RC(=O)R', where R and R' can be a variety of carbon-containing substituents. Ketones and aldehydes are simple compounds that contain a carbonyl group (a carbon-oxygen double bond). They are considered "simple" because they do not have reactive groups like −OH or −Cl attached directly to the carbon atom in the carbonyl group, as in carboxylic acids containing −COOH.[1] Many ketones are known and many are of great importance in industry and in biology. Examples include many sugars (ketoses) and the industrial solvent acetone, which is the smallest ketone. Nomenclature and etymology[edit] The word ketone is derived from Aketon, an old German word for acetone.[2][3] According to the rules of IUPAC nomenclature, ketones are named by changing the suffix -ane of the parent alkane to -anone. The position of the carbonyl group is usually denoted by a number. For the most important ketones, however, traditional nonsystematic names are still generally used, for example acetone and benzophenone. These nonsystematic names are considered retained IUPAC names,[4] although some introductory chemistry textbooks use systematic names such as "2-propanone" or "propan-2-one" for the simplest ketone (CH3−CO−CH3) instead of "acetone". The common names of ketones are obtained by writing separately the names of the two alkyl groups attached to the carbonyl group, followed by "ketone" as a separate word. The names of the alkyl groups are written alphabetically. When the two alkyl groups are the same, the prefix di- is added before the name of alkyl group. The positions of other groups are indicated by Greek letters, the α-carbon being th Continue reading >>
