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Which Reaction Is Common For Both Aldehydes And Ketones?

Aldehydes And Ketones

Aldehydes And Ketones

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Pharmaceutical Chemistry I – Laboratory Experiments And Commentary

Pharmaceutical Chemistry I – Laboratory Experiments And Commentary

Aldehydes and ketones are simple compounds which contain a carbonyl group, where a carbon-oxygen double bond is found. The oxygen atom in a double bond is called oxo group. Aldehydes have at least one hydrogen attached to the carbon atom of the carbonyl. Ketones have two alkyl and/or aryl groups as substituents on the carbonyl carbon atom. The aldehyde group is also called formyl substituent. In the IUPAC system of nomenclature aliphatic aldehydes are named substitutively using the characteristic suffix -al. Since an aldehyde carbonyl group must always lie at the terminal of a carbon chain, it is position 1 by default, and therefore defines the numbering direction. Many aldehydes also have common names derived from the common names of the corresponding carboxylic acid. In some cases the carbaldehyde suffix is used, in which case the carbonyl carbon atom do not form a part of the basic carbon chain. Aliphatic ketones are named by replacing the final -e of the corresponding alkane with the suffix -one. A ketone carbonyl function may be located anywhere within a chain or ring, and its position is given by a locator number. Chain numbering normally starts from the end nearest the carbonyl group. Common names of ketones are formed by adding the word ketone to the names of the alkyl or aryl groups attached to the carbonyl carbon atom. The properties of the compounds are determined by the electron structure of the carbonyl group. The carbon atom of the carbonyl group is sp2 hybridized; the oxygen and both atoms attached to the carbonyl carbon atom are in the same plane. The greater electronegativity of oxygen results in polarization of the double bond, with partial positive charge on the carbon and partial negative charge on the oxygen. As a consequence, the carbon atom is ele Continue reading >>

Flash Version 9,0 Or Greater Is Required

Flash Version 9,0 Or Greater Is Required

Sort Reacting the 2 CBS molecules with For ketones having the general structure C6H5COR gives what product(s)? • The (S)-CBS reagent delivers hydride (H:-) from the front side of the C=O. This generally affords the R alcohol as the major product. • The (R)-CBS reagent delivers hydride (H:-) from the back side of the C=O. This generally affords the S alcohol as the major product. Highly enantioselective (forms almost 97% of the correct enantiomer usually) Oxidation of Aldehydes The most common oxidation reaction of carbonyl compounds is the oxidation of aldehydes to carboxylic acids. A variety of oxidizing agents can be used, including CrO₃, Na₂Cr₂O₇, K₂Cr₂O₇, and KMnO₄. Cr⁶⁺ reagents are also used to oxidize 1° and 2° alcohols, as discussed in Section 12.12. Because ketones have no H on the carbonyl carbon, they do not undergo this oxidation reaction. Aldehydes are oxidized selectively in the presence of other functional groups using silver(I) oxide in aqueous ammonium hydroxide (Ag₂O in NH₄OH). Acetylide Anions acetylide anions discussed in Chapter 11 are another example of organometallic compounds. These reagents are prepared by an acid-base reaction of an alkyne with a base such as NaNH₂ or NaH. We can think of these compounds as organosodium reagents. Because sodium is even more electropositive (less electronegative) than lithium, the C-Na bond of these organosodium compounds is best described as ionic, rather than polar covalent. Synthesize 3-pentanol [(CH₃CH₂)₂CHOH] by a Grignard reaction locate the carbon bonded to the OH group, and then break the molecule into two components at this carbon. Thus, retrosynthetic analysis shows that one of the ethyl groups on this carbon come from a Grignard reagent (CH₃CH₂MgX), and the re Continue reading >>

Overview Of Reactions Of Aldehydes And Ketones

Overview Of Reactions Of Aldehydes And Ketones

Reaction with C nucleophiles: Reaction with N nucleophiles: Reaction with O nucleophiles: Oxidation Reactions Reduction to Hydrocarbons (review of Chapter 12) (acidic conditions) Zn(Hg) in HCl reduced the C=O into-CH2- Wolff-Kishner Reduction (basic conditions) NH2NH2 / KOH / ethylene glycol (a high boiling solvent) reduces the C=O into -CH2- Overview These reduction methods do not reduce C=C, C≡C or -CO2H The choice of method should be made based on the tolerance of other functional groups to the acidic or basic reaction conditions. (review of Chapter 15) Reaction type: Nucleophilic Addition Summary Aldehydes and ketones are most readily reduced with hydride reagents. The reducing agents LiAlH4 and NaBH4 act as a source of 4 x H- (hydride ion). Overall 2 H atoms are added across the C=O to give H-C-O-H. Hydride reacts with the carbonyl group, C=O, in aldehydes or ketones to give alcohols. The substituents on the carbonyl dictate the nature of the product alcohol. Reduction of methanal (formaldehyde) gives methanol. Reduction of other aldehydes gives primary alcohols. Reduction of ketones gives secondary alcohols. The acidic work-up converts an intermediate metal alkoxide salt into the desired alcohol via a simple acid base reaction. Related Reactions Reaction of RLi and RMgX with aldehydes and ketones Cyanohydrin Formation Reaction type: Nucleophilic Addition Summary Cyanide adds to aldehydes and ketones to give a cyanohydrin. The reaction is usually carried out using NaCN or KCN with HCl. HCN is a fairly weak acid, but very toxic. The reaction is useful since the cyano group can be converted into other useful functional groups (-CO2H or -CH2NH2) (review of Chapter 14) Reaction type: Nucleophilic Addition Summary Organolithium or Grignard reagents react with the carb Continue reading >>

Aldehydes, Ketones, Carboxylic Acids, And Esters

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 >>

Chapter 16: Aldehydes And Ketones (carbonyl Compounds)

Chapter 16: Aldehydes And Ketones (carbonyl Compounds)

The Carbonyl Double Bond Both the carbon and oxygen atoms are hybridized sp2, so the system is planar. The three oxygen sp2 AO’s are involved as follows: The two unshared electorn pairs of oxygen occupy two of these AO’s, and the third is involved in sigma bond formation to the carbonyl carbon. The three sp2 AO’s on the carbonyl carbon are involved as follows: One of them is involved in sigma bonding to one of the oxygen sp2 AO’s, and the other two are involved in bonding to the R substituents. The 2pz AO’s on oxygen and the carbonyl carbon are involved in pi overlap, forming a pi bond. The pi BMO, formed by positive overlap of the 2p orbitals, has a larger concentration of electron density on oxygen than carbon, because the electrons in this orbital are drawn to the more electronegative atom, where they are more highly stabilized. This result is reversed in the vacant antibonding MO. As a consequence of the distribution in the BMO, the pi bond (as is the case also with the sigma bond) is highly polar, with the negative end of the dipole on oxygen and the positive end on carbon. We will see that this polarity, which is absent in a carbon-carbon pi bond, has the effect of strongly stabilizing the C=O moiety. Resonance Treatment of the Carbonyl Pi Bond 1.Note that the ionic structure (the one on the right side) has one less covalent bond, but this latter is replaced with an ionic bond (electrostatic bond). 2.This structure is a relatively “good” one, therefore, and contributes extensively to the resonance hybrid, making this bond much more thermodynamically stable than the C=C pi bond, for which the corresponding ionic structure is much less favorable (negative charge is less stable on carbon than on oxygen). 3.The carbonyl carbon therefore has extensive car Continue reading >>

Carbonyl Functional Groups

Carbonyl Functional Groups

Chapter 15 - Carbonyl Compounds usually subdivided into two families: aldehydes and ketones both R groups are C or H carboxyl derivatives X is some electronegative element (halogen, O, N, S, others) The Carbonyl Group - Structure and Properties polar C=O double bond O is nucleophilic reacts with acids & electrophiles C is electrophilic reacts with Lewis bases and nucleophiles alpha-C-H position is acidic (pKa ~ 20) Aldehyde Nomenclature IUPAC: alkanal -al suffix, with carbonyl assumed #1 in parent chain -carbaldehyde suffix (if aldehyde can't be part of the parent) e.g., cyclohexanecarbaldehyde common nomenclature: formaldehyde acetaldehyde propionaldehyde butyraldehyde benzaldehyde Ketone Nomenclature IUPAC: alkanone -one suffix, with number -oxo- prefix if necessary e.g., 4-oxopentanal common nomenclature: dialkyl ketone acetone acetophenone benzophenone acyl- as prefix e.g., acetyl or benzoyl, as in acetylcyclopropane Precedence Order of Functional Groups decides which gets to be the parent compound (suffix) lower functional groups must be named as substituents (prefixes) carboxylic acid aldehyde ketone alcohol amine thiol Characteristic Properties polar H-bond acceptors, but not H-bond donors Mass spec shows alpha cleavage (stable acylium ion RCO+) or McLafferty rearrangement (split between alpha and beta carbons) NMR shows aldehyde C-H at 9-10 ppm, C=O at 180-210 ppm IR shows strong C=O stretch at 1600-1800 cm-1 exact position depends on ring strain, conjugation UV shows weak n -> pi* at ~ 300 nm and pi -> pi* at ~ 200 nm exact position and strength of the absorption depends on conjugation Nucleophilic Addition to Carbonyls the major reaction of carbonyl compounds General Trends: aldehydes more reactive than ketones (due to steric hindrance with ketones) aromatic c Continue reading >>

Aldehydes And Ketones

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 >>

Reagents For Modifying Aldehydes And Ketones—section 3.3

Reagents For Modifying Aldehydes And Ketones—section 3.3

Aldehydes and ketones are present in a number of low molecular weight molecules such as drugs, steroid hormones, reducing sugars and metabolic intermediates (e.g., pyruvate and α-ketoglutarate). Except for polysaccharides containing free reducing sugars, however, biopolymers generally lack aldehyde and ketone groups. Even those aldehydes and ketones that are found in the open-ring form of simple carbohydrates are usually in equilibrium with the closed-ring form of the sugar. The infrequent occurrence of aldehydes and ketones in biomolecules has stimulated the development of techniques to selectively introduce these functional groups, thus providing unique sites for chemical modification and greatly extending the applications of the probes found in this section. Fluorescent modification of aldehyde or carboxylic acid groups in carbohydrates is also frequently utilized for their analysis by HPLC, capillary electrophoresis and other methods. Periodate Oxidation The most common method for introducing aldehydes and ketones into polysaccharides and glycoproteins (including antibodies) is by periodate-mediated oxidation of vicinal diols. These introduced aldehydes and ketones can then be modified with fluorescent or biotinylated hydrazine, hydroxylamine or amine derivatives to label the polysaccharide or glycoprotein. For example, some of the hydrazine derivatives described in this section have been used to detect periodate-oxidized glycoproteins in gels. The Pro-Q Emerald 300 and Pro-Q Emerald 488 Glycoprotein Gel and Blot Stain Kits (P21855, P21857, M33307; Detecting Protein Modifications—Section 9.4) are based on periodate oxidation of glycoproteins and subsequent labeling with a Pro-Q Emerald dye. Periodate oxidation of the 3'-terminal ribose provides one of the few met Continue reading >>

1. Nomenclature Of Aldehydes And Ketones

1. Nomenclature Of 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. If neither is hydrogen, the compound is a ketone. The IUPAC system of nomenclature assigns a characteristic suffix to these classes, al to aldehydes and one to ketones. For example, H2C=O is methanal, more commonly called formaldehyde. Since an aldehyde carbonyl group must always lie at the end of a carbon chain, it is by default position #1, and therefore defines the numbering direction. A ketone carbonyl function may be located anywhere within a chain or ring, and its position is given by a locator number. Chain numbering normally starts from the end nearest the carbonyl group. In cyclic ketones the carbonyl group is assigned position #1, and this number is not cited in the name, unless more than one carbonyl group is present. If you are uncertain about the IUPAC rules for nomenclature you should review them now. Examples of IUPAC names are provided (in blue) in the following diagram. Common names are in red, and derived names in black. In common names carbon atoms near the carbonyl group are often designated by Greek letters. The atom adjacent to the function is alpha, the next removed is beta and so on. Since ketones have two sets of neighboring atoms, one set is labeled α, β etc., and the other α', β' etc. Very simple ketones, such as propanone and phenylethanone (first two examples in the right column), do not require a locator number, since there is only one possible site for a ketone carbonyl function. Likewise, locator numbers are omitted for the simple dialdehyde at t Continue reading >>

Reactions Of Aldehydes And Ketones

Reactions Of Aldehydes And Ketones

Aldehydes and ketones undergo a variety of reactions that lead to many different products. The most common reactions are nucleophilic addition reactions, which lead to the formation of alcohols, alkenes, diols, cyanohydrins (RCH(OH)C&tbond;N), and imines R 2C&dbond;NR), to mention a few representative examples. The main reactions of the carbonyl group are nucleophilic additions to the carbon‐oxygen double bond. As shown below, this addition consists of adding a nucleophile and a hydrogen across the carbon‐oxygen double bond. Due to differences in electronegativities, the carbonyl group is polarized. The carbon atom has a partial positive charge, and the oxygen atom has a partially negative charge. Aldehydes are usually more reactive toward nucleophilic substitutions than ketones because of both steric and electronic effects. In aldehydes, the relatively small hydrogen atom is attached to one side of the carbonyl group, while a larger R group is affixed to the other side. In ketones, however, R groups are attached to both sides of the carbonyl group. Thus, steric hindrance is less in aldehydes than in ketones. Electronically, aldehydes have only one R group to supply electrons toward the partially positive carbonyl carbon, while ketones have two electron‐supplying groups attached to the carbonyl carbon. The greater amount of electrons being supplied to the carbonyl carbon, the less the partial positive charge on this atom and the weaker it will become as a nucleus. The addition of water to an aldehyde results in the formation of a hydrate. The formation of a hydrate proceeds via a nucleophilic addition mechanism. 1. Water, acting as a nucleophile, is attracted to the partially positive carbon of the carbonyl group, generating an oxonium ion. Acetal formation reacti Continue reading >>

The Silver Mirror Test

The Silver Mirror Test

An exciting test to differentiate between aldose and ketose sugars Bernhard Christian Gottfried Tollens (1841-1918) was a German chemist whose name has been recognised through the silver mirror test using Tollens' reagent. He developed this test to differentiate between aldose and ketose sugars. Tollens' reagent is an alkaline solution of ammoniacal silver nitrate and is used to test for aldehydes. Silver ions in the presence of hydroxide ions come out of solution as a brown precipitate of silver(I) oxide, Ag2O(s). This precipitate dissolves in aqueous ammonia, forming the diamminesilver(I) ion, [Ag(NH3)2]+. Ketones do not react with Tollens' reagent. 2Ag+ (aq) + 2OH- (aq) Ag2 O(s) + H2 O(l) Ag2 O(s) + 4NH3 (aq) + H2 O(l) 2[Ag(NH3)2]+ (aq) + 2OH- (aq) The practical instructions and safety information for this experiment have been replaced with the updated version on the Learn Chemistry website. Adding the ammonia to the silver nitrate solution makes the silver ion less susceptible to reduction, which produces silver in a more controlled manner. Ag+ + e-→ Ag E° = +0.799 V Ag(NH3)2+ + e-→ Ag + 2NH3E° = +0.373 V The half-equations indicate that ammonia forms a complex with the silver ion, which is more difficult to reduce than the silver ion. This is because silver ions form more stable complexes with NH3 than with water. If silver nitrate is used without ammonia, the silver ion is reduced so quickly that colloidal silver metal would appear. The solution would become a black, cloudy liquid. Basic conditions are necessary because glucose is oxidised more easily under basic conditions: RCHO + H2O → RCOOH + 2H+ + 2e- Tollens' reagent and other similar tests, eg Benedict's and Fehling's, will test for aldehydes but will not identify individual compounds. They all rely Continue reading >>

Chapter 5 Aldehydes And Ketones

Chapter 5 Aldehydes And Ketones

5.1 Introduction H Aldehydes have a -C=O functional group. An aldehyde requires that at least one of the bonds on the C=O group is a hydrogen atom. When the carbonyl group (C=O) has two C atoms bonded to it is classified as a ketone. 5.2 Naming Aldehydes and Ketones Systematic: methanal ethanal propanal butanal Common: formaldehyde acetaldehyde You should know the common names! They are more commonly used than the systematic names. Ketones: Systematic: propanone 1,3-dihydroxypropanone 3-heptanone Common: acetone dihydroxyacetone(DHA) The ketone is assigned a number on the chain starting from whichever end gives the smaller number. It takes priority over branches off the chain. Methanal (formaldehyde) is a commonly used preservative for biological specimens although concern about it being a mild carcinogen has prompted efforts to reduce its use and to provide very good ventilation when it is used to minimize exposure. Propanone (acetone) is commonly used in nail polish remover. It is also a metabolic product sometimes formed by diabetics who are not controlling their blood sugar. It is readily detected, because it makes the breath smell like nail polish remover or “fruityâ€, not a normal situation! This condition is called ketosis, indicating the presence of ketones in the blood. This condition is also commonly associated with blood acidosis and the combined condition is referred to as ketoacidosis. Dihydroxyacetone is the active ingredient in some sunless sun tanning lotions. It reacts with amino acids in the skin to form melaninoids which have a brown color. In its original formulation, it gave an orange tan but improvements in formulations have improved its esthetics considerably. It absorbs primarily in the UV-A range (320-400 nm) but only with a typical SPF Continue reading >>

A Simple Formula For 7 Important Aldehyde/ketone Reactions

A Simple Formula For 7 Important Aldehyde/ketone Reactions

Here’s one thing you’re going to learn about reactions of aldehydes and ketones. There’s a LOT of repetition in the mechanism. You’ll see this in more detail soon, but let’s get a taste of how things work. Imagine you’re a guitar player. And someone tells you that you need to learn how to play 14 songs… ASAP. Sounds scary, right? But what if you then found that each of these songs had the exact same sequence of chords, and only differed in their lyrics? That’s a lot easier. We’re going to go through 14 reactions in this post. BUT… before you run away screaming… it’s really just ONE reaction… that works on both aldehydes and ketones… that has seven different variants. That sounds a lot simpler, right? All of the following reactions listed here proceed through the exact same sequence: Addition of nucleophile to the carbonyl carbon. Protonation of the oxygen. The reactions are the following: Grignard reaction Addition of organolithiums Reduction of aldehydes and ketones with NaBH4 and LiAlH4 Addition of (-)CN to give cyanohydrins This works for both aldehydes and ketones (even though just aldehydes are shown here). Apologies – big image. All we’re doing here is changing the identity of the nucleophile! It’s like having a formula, and all we’re doing is plugging a different nucleophile into the formula. Do you see how knowing the mechanisms here is going to make your life much easier? Because instead of having to keep track of 14 different reactions (7 different nucleophiles with aldehydes or ketones) you’re really just learning ONE reaction, with 7 different nucleophiles and two variants (aldehydes/ketones). Thanks for reading! James Organic Chemistry 2 builds on the concepts from Org 1 and introduces a lot of new reactions. Here is an Continue reading >>

Synthesis Of Aldehydes And Ketones

Synthesis Of Aldehydes And Ketones

Name Reactions Fukuyama Coupling Grignard Reaction Grignard Reaction Seebach Umpolung Stetter Synthesis Recent Literature Carboxylic acids were converted directly in good yields into ketones using excess alkyl cyanocuprates (R2CuLi•LiCN). A substrate with a stereocenter α to the carboxylic acid was converted with very little loss of enantiomeric purity. A variety of functional groups were tolerated including aryl bromides. This direct transformation involves a relatively stable copper ketal tetrahedral intermediate. D. T Genna, G. H. Posner, Org. Lett., 2011, 13, 5358-5361. Unsymmetrical dialkyl ketones can be prepared by the nickel-catalyzed reductive coupling of carboxylic acid chlorides or (2-pyridyl)thioesters with alkyl iodides or benzylic chlorides. Various functional groups are tolerated, including common nitrogen protecting groups and C-B bonds. Even hindered ketones flanked by tertiary and secondary centers can be formed. A. C. Wotal, D. J. Weix, Org. Lett., 2012, 14, 1363-1365. N-acylazetidines are bench-stable, readily available amide acylating reagents, in which the reactivity is controlled by amide pyramidalization and strain of the four-membered ring. A general and highly chemoselective synthesis of ketones by the addition of organometallics to N-acylazetidines via stable tetrahedral intermediates offers wide substrate scope and exquisite selectivity for the ketone products. C. Liu, M. Achtenhagen, M. Szostak, Org. Lett., 2016, 18, 2375-2378. A range of unsymmetrical ketones has been prepared in good yields from aldehydes in one simple synthetic operation by addition of organolithium compounds followed by an oxidation using N-tert-butylphenylsulfinimidoyl chloride. J. J. Crawford, K. W. Hederson, W. J. Kerr, Org. Lett., 2006, 8, 5073-5076. Visible light Continue reading >>

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