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
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 >>
Aldehydes, Ketones, Carboxylic Acids, And Esters
Learning Objectives 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 Continue reading >>
Annulative Π-extension (apex): Rapid Access To Fused Arenes, Heteroarenes, And Nanographenes
Abstract The annulative π-extension (APEX) reaction has the potential to have a tremendous impact on the fields of materials science and bioimaging, as well as on the pharmaceutical/agrochemical industries, since it allows access to fused aromatic systems from relatively simple aromatic compounds in a single step. Typically, an APEX reaction facilitates a one-pot π-extension without the need to prefunctionalize the aromatic compounds. This advantageous feature is extremely useful for tuning and modifying molecular properties in the last step of a synthesis. In this Review, the progress and applications of APEX reactions of unfunctionalized arenes and heteroarenes are described. Continue reading >>
Fragrance Sample? Aldehydes And Ketones
Formaldehyde and acetone are immediately associated with nail hardeners and nail enamel remover. In chemical terms, these substances belong to the substance class of aldehydes and ketones - which are well-known molecules in cosmetic products like e.g. preservatives, perfumes or essential oils. Aldehydes and ketones are oxygen-containing hydrocarbons and can be found in abundance either in natural surroundings but also in combination with chemical processes. They are formed with the oxidation of alcohol for instance. The low molecular molecules are used in cosmetic products because of their flowery notes and solvent characteristics. Aldehydes and ketones also are known for their chemical reactivity which is the reason for a strong antimicrobial activity. Formaldehyde is not equipped with an agreeable fragrance though, as a matter of fact even in small concentrations it has quite a disagreeable pungent and acrid smell that irritates eyes and respiratory tract. Due to the high reactivity of formaldehyde with nitrogen-containing substances like proteins respectively amino acids, it is used as a disinfecting agent and preservative. formaldehyde Since formaldehyde has meanwhile been classified as a carcinogenic substance, its use in cosmetic products is subject to strong restrictions (KVO - German Cosmetic Decree): "Every finished product containing formaldehyde and those that release formaldehyde are subject to be labeled "containing formaldehyde" as far as the concentration of formaldehyde in the finished product exceeds 0.05 %." Nail hardeners may contain concentrations of about 5 % though. Once applied on the nails it cross-links with the protein structures of the keratin in the nails similar to cross-linkage processes in plastics manufacturing. Formaldehyde use declining Continue reading >>
Aucl3-catalyzed Benzannulation: Synthesis Of Naphthyl Ketone Derivatives From O-alkynylbenzaldehydes With Alkynes
Abstract The reaction of o-alkynylbenzaldehydes 1 and alkynes 2 in the presence of a catalytic amount of AuCl3 in (CH2Cl)2 at 80 °C gave naphthyl ketone products in high yields. The AuCl3-catalyzed formal [4 + 2] benzannulation proceeds most probably through the coordination of the triple bond of 1 to AuCl3, the formation of benzo[c]pyrylium auric ate complex via the nucleophilic addition of the carbonyl oxygen atom, the Diels−Alder addition of alkynes 2 to the auric ate complex, and subsequent bond rearrangement. Similarly, the AuCl3-catalyzed reactions of o-alkynylacetophenone and o-alkynylbenzophenone with phenylacetylene afforded the corresponding naphthyl ketone products in good yields. Continue reading >>
Carbanion
Carbanion, any member of a class of organic compounds in which a negative electrical charge is located predominantly on a carbon atom. Carbanions are formally derived from neutral organic molecules by removal of positively charged atoms or groups of atoms, and they are important chiefly as chemical intermediates—that is, as substances used in the preparation of other substances. Important industrial products, including useful plastics, are made using carbanions. The simplest carbanion, the methide ion (CH-3 ), is derived from the organic compound methane (CH4) by a loss of a proton (hydrogen ion, H+) as shown in the following chemical equation: in which the symbols C and H represent, respectively, carbon and hydrogen atoms; the subscripts indicate the numbers of atoms of each kind included in the molecules; the superscript plus and minus signs indicate, respectively, positive and negative charges; and the double arrows indicate that the reaction shown can proceed in either the forward or the reverse direction, a condition known as reversibility. Molecular structures. In discussing the structures of carbanions, one must distinguish between localized and delocalized ions. In the former, the negative charge is confined largely to one carbon atom, whereas, in the latter, it is distributed over several atoms. Localized ions. The simplest localized carbanion is the methide ion (CH-3). It is isoelectronic (it has identical electron configuration) with the neutral molecule ammonia (formula NH3, N being the chemical symbol for the nitrogen atom). The geometry of the methide ion is best represented by a pyramid with the carbon atom at the apex, a structure similar to that of the ammonia molecule. Both structures are shown below: in which the solid lines represent bonds between 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 >>
Organocatalytic Asymmetric Α-bromination Of Aldehydes And Ketones
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Efficient Hydrogenation Of Ketones And Aldehydes Catalyzed By Well-defined Iron(ii) Pnp Pincer Complexes: Evidence For An Insertion Mechanism
Go to: Introduction The catalytic reduction of polar multiple bonds via molecular hydrogen plays a significant role in modern synthetic organic chemistry. This reaction is excellently performed by many transition metal complexes containing noble metals such as ruthenium, rhodium, or iridium.1 However, the limited availability of precious metals, their high price, and their toxicity diminish their attractiveness in the long run, and more economical and environmentally friendly alternatives have to be found. In this respect, the preparation of well-defined iron-based catalysts of comparable activity would be desirable.2 Iron is the most abundant transition metal in the earth’s crust and is ubiquitously available. Accordingly, it is not surprising that the field of iron-catalyzed hydrogenations of polar multiple bonds is rapidly evolving, as shown by several recent examples.3−7 It is interesting to note that many of these hydrogenations involve ligand–metal bifunctional catalysis (metal–ligand cooperation);8 that is, the complexes contain electronically coupled hydride and acidic hydrogen atoms as a result of heterolytic dihydrogen cleavage that may be transferred to polar unsaturated substrates in an outer-sphere fashion or may be transferred via hydride migration (inner-sphere mechanism). An effective way of bond activation by metal–ligand cooperation involves aromatization/dearomatization of the ligand in pincer-type complexes. In particular, pincer ligands in which a central pyridine-based backbone is connected with −CH2PR2 and/or −CH2NR2 substituents were shown to exhibit this behavior.9 This has resulted in the development of novel and unprecedented iron catalysis where this type of cooperation plays a key role in the heterolytic cleavage of H2.4 In the Continue reading >>
Laminin Targeting Of A Peripheral Nerve-highlighting Peptide Enables Degenerated Nerve Visualization
Abstract Target-blind activity-based screening of molecular libraries is often used to develop first-generation compounds, but subsequent target identification is rate-limiting to developing improved agents with higher specific affinity and lower off-target binding. A fluorescently labeled nerve-binding peptide, NP41, selected by phage display, highlights peripheral nerves in vivo. Nerve highlighting has the potential to improve surgical outcomes by facilitating intraoperative nerve identification, reducing accidental nerve transection, and facilitating repair of damaged nerves. To enable screening of molecular target-specific molecules for higher nerve contrast and to identify potential toxicities, NP41’s binding target was sought. Laminin-421 and -211 were identified by proximity-based labeling using singlet oxygen and by an adapted version of TRICEPS-based ligand-receptor capture to identify glycoprotein receptors via ligand cross-linking. In proximity labeling, photooxidation of a ligand-conjugated singlet oxygen generator is coupled to chemical labeling of locally oxidized residues. Photooxidation of methylene blue–NP41-bound nerves, followed by biotin hydrazide labeling and purification, resulted in light-induced enrichment of laminin subunits α4 and α2, nidogen 1, and decorin (FDR-adjusted P value < 10−7) and minor enrichment of laminin-γ1 and collagens I and VI. Glycoprotein receptor capture also identified laminin-α4 and -γ1. Laminins colocalized with NP41 within nerve sheath, particularly perineurium, where laminin-421 is predominant. Binding assays with phage expressing NP41 confirmed binding to purified laminin-421, laminin-211, and laminin-α4. Affinity for these extracellular matrix proteins explains the striking ability of NP41 to highlight deg Continue reading >>
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Acetone Peroxide
Acetone peroxide is an organic peroxide and a primary high explosive. It is produced by the oxidation of acetone to yield a mixture of linear monomer and cyclic dimer, trimer, and tetramer forms. The trimer is known as triacetone triperoxide (TATP) or tri-cyclic acetone peroxide (TCAP). Acetone peroxide takes the form of a white crystalline powder with a distinctive bleach-like odor (when impure) and can explode if subjected to heat, friction, static electricity, strong UV radiation or shock. As a non-nitrogenous explosive, TATP has historically been more difficult to detect, and it has been used as an explosive in several terrorist attacks since 2001. History[edit] Acetone peroxide (specifically, triacetone triperoxide) was discovered in 1895 by Richard Wolffenstein.[2] Wolffenstein combined acetone and hydrogen peroxide, and then he allowed the mixture to stand for a week at room temperature, during which time a small quantity of crystals precipitated, which had a melting point of 97 °C.[3] In 1899 Adolf von Baeyer and Victor Villiger described the first synthesis of the dimer and described use of acids for the synthesis of both peroxides.[4] Baeyer and Villiger prepared the dimer by combining potassium persulfate in diethyl ether with acetone, under cooling. After separating the ether layer, the product was purified and found to melt at 132–133 °C.[5] They found that the trimer could be prepared by adding hydrochloric acid to a chilled mixture of acetone and hydrogen peroxide.[6] By using the depression of freezing points to determine the molecular weights of the compounds, they also determined that the form of acetone peroxide that they had prepared via potassium persulfate was a dimer, whereas the acetone peroxide that had been prepared via hydrochloric acid wa Continue reading >>
Allergic Asthma Exhaled Breath Metabolome: A Challenge For Comprehensive Two-dimensional Gas Chromatography
Allergic asthma represents an important public health issue, most common in the paediatric population, characterized by airway inflammation that may lead to changes in volatiles secreted via the lungs. Thus, exhaled breath has potential to be a matrix with relevant metabolomic information to characterize this disease. Progress in biochemistry, health sciences and related areas depends on instrumental advances, and a high throughput and sensitive equipment such as comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-ToFMS) was considered. GC×GC-ToFMS application in the analysis of the exhaled breath of 32 children with allergic asthma, from which 10 had also allergic rhinitis, and 27 control children allowed the identification of several hundreds of compounds belonging to different chemical families. Multivariate analysis, using Partial Least Squares-Discriminant Analysis in tandem with Monte Carlo Cross Validation was performed to assess the predictive power and to help the interpretation of recovered compounds possibly linked to oxidative stress, inflammation processes or other cellular processes that may characterize asthma. The results suggest that the model is robust, considering the high classification rate, sensitivity, and specificity. A pattern of six compounds belonging to the alkanes characterized the asthmatic population: nonane, 2,2,4,6,6-pentamethylheptane, decane, 3,6-dimethyldecane, dodecane, and tetradecane. To explore future clinical applications, and considering the future role of molecular-based methodologies, a compound set was established to rapid access of information from exhaled breath, reducing the time of data processing, and thus, becoming more expedite method for the clinical purposes. Continue reading >>
Proactive Repellent And Camp Perimeter Defense Against Apex Predators
BACKGROUND BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION This disclosure describes a proactive repellent and camp perimeter defense against apex predators. In an implementation, the proactive repellent is a liquid agent tuned to the particularly sensitive olfactory senses of apex predators. The example repellent is aversive to apex predators, which find the repellent distressing, threatening, repugnant, or sickening. In an implementation, the example repellent contains ingredients to catch the attention of the apex predator, while also providing olfactory aversion signals to the predator. In an implementation, the example repellent also has very low toxicity. The example repellent may also be made from environmentally safe compounds. FIG. 1 shows an example area 100, a campsite to be proactively protected by the example repellent 102 from an apex predator 104. In an implementation, the example repellent 102 can be applied around the area 100 to be proactively protected via delivery methods such as by spray, aerosol, gel, stream, or squirt apparatuses, or by foam, cloth, gauze, sponge, wick, or swab applicators. The repellent 102 then dries, emitting odors and chemicals in both liquid and dried states. Artifacts containing or covered with the example proactive repellent 102 may also be cards, tubes, sticks, balls, beads, gels, granules, stakes, and so forth, soaked, sprayed, exposed to, or impregnated with the example repellent 102, and spaced apart from each other to create a protective boundary around the campsite or other area 100. The example repellent 102 does not have to stay liquid, but may dry on the artifact, emitting repellent odors and chemicals. In an implementation, the artifacts may come pre-packaged, and previously exposed to the example repellent 102
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Organic Chemistry/ketones And Aldehydes
Aldehydes () and ketones () are both carbonyl compounds. They are organic compounds in which the carbonyl carbon is connected to C or H atoms on either side. An aldehyde has one or both vacancies of the carbonyl carbon satisfied by a H atom, while a ketone has both its vacancies satisfied by carbon. 3 Preparing Aldehydes and Ketones Ketones are named by replacing the -e in the alkane name with -one. The carbon chain is numbered so that the ketone carbon, called the carbonyl group, gets the lowest number. For example, would be named 2-butanone because the root structure is butane and the ketone group is on the number two carbon. Alternatively, functional class nomenclature of ketones is also recognized by IUPAC, which is done by naming the substituents attached to the carbonyl group in alphabetical order, ending with the word ketone. The above example of 2-butanone can also be named ethyl methyl ketone using this method. If two ketone groups are on the same structure, the ending -dione would be added to the alkane name, such as heptane-2,5-dione. Aldehydes replace the -e ending of an alkane with -al for an aldehyde. Since an aldehyde is always at the carbon that is numbered one, a number designation is not needed. For example, the aldehyde of pentane would simply be pentanal. The -CH=O group of aldehydes is known as a formyl group. When a formyl group is attached to a ring, the ring name is followed by the suffix "carbaldehyde". For example, a hexane ring with a formyl group is named cyclohexanecarbaldehyde. Aldehyde and ketone polarity is characterized by the high dipole moments of their carbonyl group, which makes them rather polar molecules. They are more polar than alkenes and ethers, though because they lack hydrogen, they cannot participate in hydrogen bonding like Continue reading >>
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