Carbonyl group in the context of "Divalent"

The aldol reaction (aldol addition) is a reaction in organic chemistry that combines two carbonyl compounds (e.g. aldehydes or ketones) to form a new β-hydroxy carbonyl compound. Its simplest form might involve the nucleophilic addition of an enolized ketone to another:

These products are known as aldols, from the aldehyde + alcohol, a structural motif seen in many of the products. The use of aldehyde in the name comes from its history: aldehydes are more reactive than ketones, so that the reaction was discovered first with them.

In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many forms of polymerization and different systems exist to categorize them.

In chemical compounds, polymerization can occur via a variety of reaction mechanisms that vary in complexity due to the functional groups present in the reactants and their inherent steric effects. In more straightforward polymerizations, alkenes form polymers through relatively simple radical reactions; in contrast, reactions involving substitution at a carbonyl group require more complex synthesis due to the way in which reactants polymerize.

In organic chemistry, a ketone /ˈkiːtoʊn/ is an organic compound with the structure R−C(=O)−R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group −C(=O)− (a carbon-oxygen double bond C=O). A ketone derived from an alkane is an alkanone. The simplest ketone is acetone (where R and R' are methyl), with the formula (CH₃)₂CO. Many ketones are of great importance in biology and industry. Examples include many sugars (ketoses), many steroids, e.g., testosterone, and the solvent acetone.

A diol is a chemical compound containing two hydroxyl groups (−OH groups). An aliphatic diol may also be called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified. They are used as protecting groups of carbonyl groups, making them essential in synthesis of organic chemistry.

The most common industrial diol is ethylene glycol. Examples of diols in which the hydroxyl functional groups are more widely separated include 1,4-butanediol HO−(CH₂)₄−OH and propylene-1,3-diol, or beta propylene glycol, HO−CH₂−CH₂−CH₂−OH.

In organic chemistry, an addition reaction is an organic reaction in which two or more molecules combine to form a larger molecule called the adduct.

An addition reaction is limited to chemical compounds that have multiple bonds. Examples include a molecule with a carbon–carbon double bond (an alkene) or a triple bond (an alkyne). Another example is a compound that has rings (which are also considered points of unsaturation). A molecule that has carbon—heteroatom double bonds, such as a carbonyl group (C=O) or imine group (C=N), can undergo an addition reaction because its double-bond.

In organic chemistry, an aldol is a structure consisting of a hydroxy group (-OH) two carbons away from either an aldehyde or a ketone. The name combines the suffix 'ol' from the alcohol and the prefix depending on the carbonyl group, either 'ald' for an aldehyde, or 'ket' for a ketone, in which case it referred to as a 'ketol'. An aldol may also use the term β-hydroxy aldehyde (or β-hydroxy ketone for a ketol). The term "aldol" may refer to 3-hydroxybutanal.

Aldols are the product of a carbon-carbon bond-formation reaction, giving them wide applicability as a precursor for a variety of other compounds.

An isopeptide bond is a type of amide bond formed between a carboxyl group of one amino acid and an amino group of another. An isopeptide bond is the linkage between the side chain amino or carboxyl group of one amino acid to the α-carboxyl, α-amino group, or the side chain of another amino acid. In a typical peptide bond, also known as eupeptide bond, the amide bond always forms between the α-carboxyl group of one amino acid and the α-amino group of the second amino acid. Isopeptide bonds are rarer than regular peptide bonds. Isopeptide bonds lead to branching in the primary sequence of a protein. Proteins formed from normal peptide bonds typically have a linear primary sequence.

Amide bonds, and thus isopeptide bonds, are stabilized by resonance (electron delocalization) between the carbonyl oxygen, the carbonyl carbon, and the nitrogen atom. The bond strength of an isopeptide bond is similar to that of a peptide due to the similar bonding type. The bond strength of a peptide bond is around 300 kJ/mol, or about 70 kcal/mol.

In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a pericyclic reaction with a concerted mechanism. More specifically, it is classified as a thermally allowed [4+2] cycloaddition with Woodward–Hoffmann symbol [_π4_s + _π2_s]. It was first described by Otto Diels and Kurt Alder in 1928. For the discovery of this reaction, they were awarded the Nobel Prize in Chemistry in 1950. Through the simultaneous construction of two new carbon–carbon bonds, the Diels–Alder reaction provides a reliable way to form six-membered rings with good control over the regio- and stereochemical outcomes. Consequently, it has served as a powerful and widely applied tool for the introduction of chemical complexity in the synthesis of natural products and new materials. The underlying concept has also been applied to π-systems involving heteroatoms, such as carbonyls and imines, which furnish the corresponding heterocycles; this variant is known as the hetero-Diels–Alder reaction. The reaction has also been generalized to other ring sizes, although none of these generalizations have matched the formation of six-membered rings in terms of scope or versatility. Because of the negative values of ΔH° and ΔS° for a typical Diels–Alder reaction, the microscopic reverse of a Diels–Alder reaction becomes favorable at high temperatures, although this is of synthetic importance for only a limited range of Diels–Alder adducts, generally with some special structural features; this reverse reaction is known as the retro-Diels–Alder reaction.

An aldose is a monosaccharide (a simple sugar) with a carbon backbone chain with a carbonyl group on the endmost carbon atom, making it an aldehyde, and hydroxyl groups connected to all the other carbon atoms. Aldoses can be distinguished from ketoses, which have the carbonyl group away from the end of the molecule, and are therefore ketones.