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Ketone Synthesis From Alkene

Synthesis Of Ketones By Cleavage Of Alkenes

Synthesis Of Ketones By Cleavage Of Alkenes

Name Reactions Recent Literature The OsO4-catalyzed direct oxidation of olefins via the carbon-carbon cleavage of an osmate ester by the action of oxone allows the preparation of ketones or carboxylic acids in high yields. This method should be applicable as an alternative to ozonolysis. B. R. Travis, R. S. Narayan, B. Borhan, J. Am. Chem. Soc., 2002, 124, 3824-3825. N-hydroxyphthalimide (NHPI) catalyzes a metal-free, aerobic oxidative cleavage of olefins. This methodology avoids the use of toxic metals or overstoichiometric amounts of traditional oxidants, showing good economical and environmental advantages. Based on the experimental observations, a plausible mechanism is proposed. R. Lin, F. Chen, N. Jiao, Org. Lett., 2012, 14, 4158-4161. A mild and operationally simple protocol for the selective aerobic oxidation of aromatic olefins to carbonyl compounds is catalyzed by a Fe(III) species bearing a pyridine bisimidazoline ligand at 1 atm of O2. The method cleaves α- and β-substituted styrenes to afford benzaldehydes and aromatic ketones in high yields with excellent chemoselectivity and very good functional group tolerance. A. Gonzalez-de-Castro, J. Xiao, J. Am. Chem. Soc., 2015, 137, 8206-8218. In a 2,2-azobis(isobutyronitrile)-catalyzed oxidative cleavage of gem-disubstituted alkenes with molecular oxygen as the oxidant, carbonyl compounds were obtained as the desired products in high yield under mild conditions. G.-Z. Wang, X.-L. Li, J.-J. Dai, H.-J. Xu, J. Org. Chem., 2014, 79, 7220-7225. A gold(I)-catalyzed oxidative cleavage of alkenes with tert-butyl hydrogenperoxide (TBHP) as the oxidant in the presence of neocuproine afforded ketones or aldehydes as products. D. Xing, B. Guan, G. Cai, Z. Fang, L. Yang, Z. Shi, Org. Lett., 2006, 8, 693-696. Specific oxidati Continue reading >>

Enolates With Aldehydes And Ketones

Enolates With Aldehydes And Ketones

Mannich Reaction This is a typical example of a Mannich reaction. It involves an enolizable aldehyde or ketone, a secondary amine, formaldehyde as its aqueous solution, and catalytic HCl. The product is an amino-ketone from the addition of one molecule each of formaldehyde and the amine to the ketone. Below are shown the various stages of the Mannich reaction. 'Click' the different stages to view 3D animations of the reactions: Step 1: Imine formation Step 2: Addition of imine salt to ketone The Mannich products can be converted to enones. Enones such as that shown below, with two hydrogen atoms at the end of the double bond are called exo-methylene compounds. Whilst they are very reactive, they cannot easily be made or stored. Click the image to view the 3D animation T. F. Cummings and J. R. Shelton, J. Org. Chem, 1960, 25, 419–423. H. G. O. Alvim, E. N. da Silva Júnior and B. A. D. Neto, RSC Adv., 2014, 4, 54282–54299. 621 Continue reading >>

Synthesis Of Ketones

Synthesis Of Ketones

Like aldehydes, ketones can be prepared in a number of ways. The following sections detail some of the more common preparation methods: the oxidation of secondary alcohols, the hydration of alkynes, the ozonolysis of alkenes, Friedel‐Crafts acylation, the use of lithium dialkylcuprates, and the use of a Grignard reagent. The oxidation of secondary alcohols to ketones may be carried out using strong oxidizing agents, because further oxidation of a ketone occurs with great difficulty. Normal oxidizing agents include potassium dichromate (K 2Cr 2O 7) and chromic acid (H 2CrO 4). The conversion of 2‐propanol to 2‐propanone illustrates the oxidation of a secondary alcohol. The addition of water to an alkyne leads to the formation of an unstable vinyl alcohol. These unstable materials undergo keto‐enol tautomerization to form ketones. The hydration of propyne forms 2‐propanone, as the following figure illustrates. When one or both alkene carbons contain two alkyl groups, ozonolysis generates one or two ketones. The ozonolysis of 1,2‐dimethyl propene produces both 2‐propanone (a ketone) and ethanal (an aldehyde). Friedel‐Crafts acylations are used to prepare aromatic ketones. The preparation of acetophenone from benzene and acetyl chloride is a typical Friedel‐Crafts acylation. The addition of a lithium dialkylcuprate (Gilman reagent) to an acyl chloride at low temperatures produces a ketone. This method produces a good yield of acetophenone. Hydrolysis of the salt formed by reacting a Grignard reagent with a nitrile produces good ketone yields. For example, you can prepare acetone by reacting the Grignard reagent methyl magnesium bromide (CH 3MgBr) with methyl nitrile (CH 3C&tbond;N). Continue reading >>

Synthesis (4) – Reactions Of Alkenes

Synthesis (4) – Reactions Of Alkenes

In the last post on alkenes we covered the reactions of alkyl halides and it made out tiny little reaction map explode into a cascade. Here we’re really going to blow up our reaction map, because we’re going to talk about a second very important “hub” for synthesis – alkenes. If you haven’t already noticed…. there are a LOT of alkene reactions. Alkenes are a very versatile building block in organic chemistry, as I hope this post will make clear. This post is going to assume you’re familiar with these reactions and their products. We’re not going to go into mechanisms or other details here. The point is learning how to apply these reactions so that eventually we can plan syntheses that will take us from one functional group to another. If you need more background on these reactions by all means read this series of posts on alkenes. As we’ve said many times before, the vast majority of alkene reactions fall into the category of “addition reactions”. That is, we’re breaking a C-C π bond and forming two new bonds to carbon. The new bonds that form, of course, determine the functional group we will be creating. Beneath that, there is a second level of detail – the “regioselectivity” and “stereoselectivity” of the reaction, which you will also need to be familiar with – that will, alas, largely be ignored in our big-picture analysis in this post. The second category of alkene reactions is “oxidative cleavage”, which involves the cleavage of both C-C bonds and the formation of two new carbonyl [C=O] groups. Depending on conditions, C-H bonds directly attached to the sp2 hybridized carbons of the alkene can also be oxidized to C-OH . For the purposes of synthesis, we’ll largely be focusing on the new functional groups that are create Continue reading >>

2 Departamento De Quãmica, Facultad Experimental De Ciencias, Universidad Del Zulia,

2 Departamento De Quãmica, Facultad Experimental De Ciencias, Universidad Del Zulia,

Reviews and Accounts ARKIVOC 2013 (i) 396-417 Page 396 © ARKAT-USA, Inc. Reagents for the synthesis of alkenes from carbonyl compounds: applications in the synthesis of terpenoid compounds William J. Vera, 1 Manuel S. Laya, 1 Po S. Poon, 1 Ajoy K. Banerjee, and Elvia V. Cabrera 2 1 Instituto Venezolano de Investigaciones CientÃficas (IVIC), Centro de QuÃmica, Apartado-21827, Caracas-1020A, Venezuela 2 Departamento de QuÃmica, Facultad Experimental de Ciencias, Universidad del Zulia, Maracaibo, Venezuela Email: [email protected] Abstract The carbon-carbon double bond has been introduced by replacing carbonyl group employing various reagents in several decalones and tetralones. The resulting unsaturated compounds have been utilized for the synthesis of natural products related to diterpenes triptolide, taxodione and sesquiterpenes, herbertene, cuauhtemone, warburganal, drim-8-en-7-one, occidol, mansonone F and biflorine. Keywords: Halide, tosylate, mesylate, alkene, dimethylformamide, 2,4-pentanediol Table of Contents 1. Introduction 2. Reagents for the Conversion of Carbonyl into Alkene 2.1. Lithium bromide (LiBr), lithium carbonate (Li2CO3) and dimethylformamide (DMF) 2.2. Thionyl chloride (SOCl2), phosphorus oxychloride (POCl3) and pyridine 2.3. Acid catalysed (p-toluenesulphonic acid, sulphuric acid, hydrochloric acid) dehydration 2.5. Grignard reagents (MeMgBr, Me2CHMgBr) 2.6. 2,4-Pentanediol and p-toluenesulfonic acid 3. Conclusions 4. Reference Reviews and Accounts ARKIVOC 2013 (i) 396-417 Page 397 © ARKAT-USA, Inc. 1. Introduction The formation of carbon-carbon double bond is of fundamental importance in organic synthesis because it allows the introduction of a wide variety of functional groups. As a result, many reactions and reagents have been develop Continue reading >>

Synthesis Of Carboxylic Acids

Synthesis Of Carboxylic Acids

There are many possible synthetic pathways that yield carboxylic acids. Some of these are further discussed below. Alcohols and aldehydes may be oxidized into carboxylic acids. Alkenes may be converted into carboxylic acid through oxidative cleavage of the double bond with neutral or acid permanganate, for instance. However, the alkene must contain at least one hydrogen located at the double bond, otherwise only ketones are formed. The intermediate stage of an alkene's oxidative cleavage with permanganate is a 1,2-diol. If the alkene is not water-soluble, potassium permanganate can be made soluble in an organic solvent by the application of the crown ether (a cyclic polyether) 18-crown-6. 18-crown-6 complexes the potassium ion in its center, while its periphery is non-polar. As a result, potassium ions can be dissolved in an organic solvent, such as benzene, and the negatively charged permangnate ion is, thus, forced to dissolve, as well. The reactivity of permanganate ions that are dissolved in such a way is much higher than that of permangante ions in aqueous solution, as they are not solvated. Many alkenes may be converted into carboxylic acids through ozonization and subsequent oxidative workup. In a haloform reaction with iodine, bromine, or chlorine, methyl ketones are converted into the corresponding carboxylic acid and haloform. A Gringard reaction with carbon dioxide yields a carboxylate whose carbon chain contains exactly one carbon more than the alkyl halide applied. Hydrolysis of the carboxylate leads to the formation of the carboxylic acid. The reaction is diversely applicable and proves to be an easy source of many carboxylic acids. Continue reading >>

Preparation & Reactions Of Aldehydes And Ketones, Rho & Ror'

Preparation & Reactions Of Aldehydes And Ketones, Rho & Ror'

A couple of key points: Aldehydes and Ketones both contain a carbonyl group, but are also less reactive than acid chlorides. They do NOT react with organocopper reagents and weak hydride donors (as these weak reagents are involved in their own synthesis). The reactions are addition rather than substitution as there is no leaving group. They have one less bond to an electronegative atom than acid chlorides (no chlorine!). They can be formed through reduction of Acid Chloride: If an aromatic ring is being substituted then we must use friedel crafts acylation. For Acid Chloride to Aldehyde we use Bu3SnH as a source of weak Hydride ions which displace a Cl-. We do not use a more obvious source such as LiAlH4 as this will result in the over reduction of the aldehyde into a primary alcohol. For Acid Chloride to Ketone we use R’2CuLi as a source of nucleophilic R’ group. and via reactions with Alcohols: Simply, Primary alcohols lead to Aldehydes and secondary alcohols lead to Ketones when reacted with PCC. This is oxidation. Testing Laboratory Microbiology - Air Quality - Mold Asbestos - Environmental - Lead emsl.com and finally with Alkanes: Alkanes are just as simple as alcohols – just add O3 then PPh3 for an easy reaction! Simple alkenes lead to aldehydes and more complex lead to ketones. Synthesis Summary: In short: REDUCTION From Acid Chloride to Aldehyde – Bu3SnH (as a source of H-) From Acid Chloride to Ketone – R2CuLi (as a source of R) OXIDATION From Alcohol to Aldehyde/Ketone – PCC From Alkene to Aldehyde/Ketone – O3 then PPh3 – Reactions with Carbon Nucleophiles and Hydride Donors As mentioned earlier, aldehydes and ketones do not react with weak hydride donors (eh Bu3SnH) or organocopper reagents (eg R2CuLi) – they need more powerful reagents. The Continue reading >>

Chelation-assisted Intermolecular Hydroacylation: Direct Synthesis Of Ketone From Aldehyde And 1-alkene

Chelation-assisted Intermolecular Hydroacylation: Direct Synthesis Of Ketone From Aldehyde And 1-alkene

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Alkene

Alkene

This article is about the chemical compound. For the material, see Olefin fiber. Not to be confused with Alkane or Alkyne. A 3D model of ethylene, the simplest alkene. In organic chemistry, an alkene is an unsaturated hydrocarbon that contains at least one carbon–carbon double bond.[1] The words alkene and olefin are often used interchangeably (see nomenclature section below). Acyclic alkenes, with only one double bond and no other functional groups, known as mono-enes, form a homologous series of hydrocarbons with the general formula CnH2n.[2] Alkenes have two hydrogen atoms fewer than the corresponding alkane (with the same number of carbon atoms). The simplest alkene, ethylene (C2H4), with the International Union of Pure and Applied Chemistry (IUPAC) name ethene, is the organic compound produced on the largest scale industrially.[3] Aromatic compounds are often drawn as cyclic alkenes, but their structure and properties are different and they are not considered to be alkenes.[2] Structure[edit] Bonding[edit] Ethylene (ethene), showing the pi bond in green. Like a single covalent bond, double bonds can be described in terms of overlapping atomic orbitals, except that, unlike a single bond (which consists of a single sigma bond), a carbon–carbon double bond consists of one sigma bond and one pi bond. This double bond is stronger than a single covalent bond (611 kJ/mol for C=C vs. 347 kJ/mol for C–C)[1] and also shorter, with an average bond length of 1.33 ångströms (133 pm). Each carbon of the double bond uses its three sp2 hybrid orbitals to form sigma bonds to three atoms (the other carbon and two hydrogen atoms). The unhybridized 2p atomic orbitals, which lie perpendicular to the plane created by the axes of the three sp² hybrid orbitals, combine to form th Continue reading >>

Preparations Of Aldehydes And Ketones

Preparations Of Aldehydes And Ketones

Chapter 17: Aldehydes and Ketones. Nucleophilic Addition to C=O Summary | Aldehydes and Ketones | Preparations of Aldehydes and Ketones | Reactions of Aldehydes and Ketones | Spectroscopic Analysis of Ethers | Self Assessment | Quiz | Chapter 17: Aldehydes and Ketones. Nucleophilic Addition to C=O (overview) Ozonolysis of Alkenes (review of Chapter 6) Reaction type: Electrophilic Addition Summary Overall transformation : C=C to 2C=O Reagents : ozone, O3, followed by a reducing work-up, usually Zn in acetic acid. It is convenient to view the process as cleaving the alkene into two carbonyls: The substituents on the C=O depend on the substituents on the C=C. What would be the products of the ozonolysis reactions of: (a) ethene ? (b) 1-butene ? (c) 2-butene ? (d) 2-methylpropene ? Step 1: The p electrons act as the nucleophile, attacking the ozone at the electrophilic terminal O. A second C-O is formed by the nucleophilic O attacking the other end of the C=C. Step 2: The cyclic species called the ozonide rearranges to the malozonide. Step 3: On work-up (usually Zn / acetic acid) the malozonide decomposes to give two carbonyl groups. Hydration of Alkynes (review of Chapter 9) Reaction type: Electrophilic Addition Summary Alkynes can be hydrated to form enols that immediately tautomerise to ketones Reagents: aq. acid, most commonly H2SO4, with a mercury salt Reaction proceeds via protonation to give the more stable carbocation intermediate (review). Not stereoselective since reactions proceeds via planar carbocation. Step 1: An acid / base reaction. Protonation of the alkyne to generate the more stable carbocation. The p electrons act pairs as a Lewis base. Step 2: Attack of the nucleophilic water molecule on the electrophilic carbocation creates an oxonium ion. Step 3: An a Continue reading >>

Synthesis Of Aldehydes & Ketones

Synthesis Of Aldehydes & Ketones

Aldehydes and ketones can be prepared using a wide variety of reactions. Although these reactions are discussed in greater detail in other sections, they are listed here as a summary and to help with planning multistep synthetic pathways. Please use the appropriate links to see more details about the reactions. 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 >>

Synthesis: Ketone To Alkene Conversion With C-c Bond Formation

Synthesis: Ketone To Alkene Conversion With C-c Bond Formation

Ketones are converted to alkenes accompanied by carbon-carbon bond formation through the Wittig reaction. Alternatively, this same transformation can be accomplished through the addition of a Grignard reagent to the ketone followed by dehydration of the resulting alcohol. Evaluate the four reactions below as to their potential for producing the alkene depicted in the box. Continue reading >>

Alkenes From Aldehydes And Ketones: Wittig Reaction

Alkenes From Aldehydes And Ketones: Wittig Reaction

The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide (often called a Wittig reagent) to give an alkene and triphenylphosphine oxide. The Wittig reaction was discovered in 1954 by Georg Wittig, for which he was awarded the Nobel Prize in Chemistry in 1979. It is widely used in organic synthesis for the preparation of alkenes. It should not be confused with the Wittig rearrangement. Wittig reactions are most commonly used to couple aldehydes and ketones to singly substituted phosphine ylides. With unstabilised ylides this results in almost exclusively the Z-alkene product. In order to obtain the E-alkene, stabilised ylides are used or unstabilised ylides using the Schlosser modification of the Wittig reaction can be performed. The steric bulk of the ylide 1 influences the stereochemical outcome of nucleophilic addition to give a predominance of the betaine 3 (cf. Bürgi–Dunitz angle). Note that for betaine 3 both R1 and R2 as well as PPh3+ and O− are positioned anti to one another. Carbon-carbon bond rotation gives the betaine 4, which then forms the oxaphosphetane 5. Elimination gives the desired Z-alkene 7 and triphenylphosphine oxide 6. With simple Wittig reagents, the first step occurs easily with both aldehydes and ketones, and the decomposition of the betaine (to form 5) is the rate-determining step. However, with stabilised ylides (where R1 stabilises the negative charge) the first step is the slowest step, so the overall rate of alkene formation decreases and a bigger proportion of the alkene product is the E-isomer. This also explains why stabilised reagents fail to react well with sterically hindered ketones. Mechanistic studies have focused on unstabilized ylides, because the intermedia Continue reading >>

Question: Wittig Reaction: Synthesis An Alkene ( Olefin) From The Reaction Of An Aldehyde Or A K...

Question: Wittig Reaction: Synthesis An Alkene ( Olefin) From The Reaction Of An Aldehyde Or A K...

Wittig Reaction: synthesis an alkene ( olefin) from the reaction of an aldehyde or a ketone with a phosphorous ylide ( phosphorane ). The ylide is produced from phoshonium salt with a base ( NaOH ). The alkene synthesized is trans-9-(2-phenylethenyl)anthracene. 1.) what is the overall chemical reaction? List all steps (step-by-step) with the compound names underneath. 2.) what is the Reaction Mechanism? List all steps (step-by-step) with the compound names underneath. Continue reading >>

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