Cet article est une ébauche concernant la chimie. La découverte du tamis moléculaire remonte à 1756 lorsque le terme zéolithe fut utilisé pour la première fois, pour décrire un matériel solide dont la partie d’fieser and fieser’s reagents for organic synthesis pdf pouvait être retirée par chauffage. Le terme tamis moléculaire tient son origine de J.
Plusieurs tamis moléculaires de la famille des zéolithes peuvent être régénérés par la chaleur un nombre quasi illimité de fois. H2O, CO2, SO2, H2S, C2H4, C2H6, C3H6, EtOH. N’adsorbe pas C3H8 et les chaînes carbonées plus longues. Bon pour sécher les liquides apolaires et les gaz. C4H10, alcools de type C4H9OH et thiols de type C4H9SH.
N’adsorbe pas les isomères ou les composés cycliques plus grands que C4. Fieser and Fieser, Reagents for Organic Synthesis, Vol. 1, Wiley, New York, 1967, p. Rechercher les pages comportant ce texte.
La dernière modification de cette page a été faite le 11 février 2018 à 17:11. Not to be confused with ketone bodies. R’, where R and R’ can be a variety of carbon-containing substituents. The word ketone is derived from Aketon, an old German word for acetone.
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. 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 the atom adjacent to carbonyl group. Although used infrequently, oxo is the IUPAC nomenclature for a ketone functional group. Other prefixes, however, are also used. The ketone carbon is often described as “sp2 hybridized”, a description that includes both their electronic and molecular structure.
The carbonyl group is polar because the electronegativity of the oxygen is greater than that for carbon. Thus, ketones are nucleophilic at oxygen and electrophilic at carbon. Ketones are classified on the basis of their substituents. One broad classification subdivides ketones into symmetrical and asymmetrical derivatives, depending on the equivalency of the two organic substituents attached to the carbonyl center. Many kinds of diketones are known, some with unusual properties. Ketones containing alkene and alkyne units are often called unsaturated ketones. CH2, which is useful in the Robinson annulation reaction.
CO, where n varies from 2 for cyclopropanone to the teens. Cyclohexanone, a symmetrical cyclic ketone, is an important intermediate in the production of nylon. Tautomerization is catalyzed by both acids and bases. Usually, the keto form is more stable than the enol.
This difference reflects resonance stabilization of the enolate ion that is formed upon deprotonation. The relative acidity of the α-hydrogen is important in the enolization reactions of ketones and other carbonyl compounds. An aldehyde differs from a ketone because of its hydrogen atom attached to its carbonyl group, making aldehydes easier to oxidize. Ketones don’t have a hydrogen atom bonded to the carbonyl group, and are more resistant to oxidation. The exact position of the peak depends on the substituents.