chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

, an adduct (; alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct

molecule A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

s, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species. Examples include the addition of

sodium bisulfite Sodium bisulfite (or sodium bisulphite, sodium hydrogen sulfite) is a chemical mixture with the approximate chemical formula NaHSO3. Sodium bisulfite is not a real compound, but a mixture of salts that dissolve in water to give solutions compose ...

to an

aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

to give a

sulfonate In organosulfur chemistry, a sulfonate is a salt, anion or ester of a sulfonic acid. Its formula is , containing the functional group , where R is typically an organyl group, amino group or a halogen atom. Sulfonates are the conjugate bases of ...

. It can be considered as a single product resulting from the direct combination of different molecules which comprises all atoms of the reactant molecules. Adducts often form between

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...

s and Lewis bases. A good example is the formation of adducts between the Lewis acid

borane Borane is an inorganic compound with the chemical formula . Because it tends to dimerize or form adducts, borane is very rarely observed. It normally dimerizes to diborane in the absence of other chemicals. It can be observed directly as a c ...

and the oxygen atom in the Lewis bases,

tetrahydrofuran Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water- miscible organic liquid with low viscosity. It is ...

(THF): or

diethyl ether Diethyl ether, or simply ether, is an organic compound with the chemical formula , sometimes abbreviated as . It is a colourless, highly Volatility (chemistry), volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs ...

: . Many Lewis acids and Lewis bases reacting in the gas phase or in non-aqueous solvents to form adducts have been examined in the ECW model.

Trimethylborane Trimethylborane (TMB) is a toxic, pyrophoric gas with the formula B(CH3)3 (which can also be written as Me3B, with Me representing methyl). Properties As a liquid it is colourless. The strongest line in the infrared spectrum is at 1330 cm� ...

trimethyltin chloride Trimethyltin chloride is an organotin compound with the formula . It is a white solid that is highly toxic and malodorous. It is susceptible to hydrolysis. Synthesis Trimethyltin chloride can be prepared by the Redistribution (chemistry), redistri ...

and bis(hexafluoroacetylacetonato)copper(II) are examples of Lewis acids that form adducts which exhibit

steric effects Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is generally a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape (conformational isomerism, co ...

. For example: trimethyltin chloride, when reacting with diethyl ether, exhibits steric repulsion between the

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula (whereas normal methane has the formula ). In formulas, the group is often abbreviated a ...

s on the tin and the ethyl groups on oxygen. But when the Lewis base is tetrahydrofuran, steric repulsion is reduced. The ECW model can provide a measure of these steric effects. Compounds or mixtures that cannot form an adduct because of

steric hindrance Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is generally a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivi ...

are called frustrated Lewis pairs. Adducts are not necessarily molecular in nature. A good example from

solid-state chemistry Solid-state chemistry, also sometimes referred as materials chemistry, is the study of the Chemical synthesis, synthesis, structure, and properties of solid phase materials. It therefore has a strong overlap with solid-state physics, mineralogy, cr ...

is the adducts of

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

of . The latter is a solid with an extended lattice structure. Upon formation of the adduct, a new extended phase is formed in which the gas molecules are incorporated (inserted) as

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

s of the copper atoms within the structure. This reaction can also be considered a reaction between a base and a Lewis acid where the copper atom plays the electron-receiving role and the

pi electron In chemistry, pi bonds (π bonds) are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals ...

s of the gas molecule play the electron-donating role.

Adduct ions

An adduct ion is formed from a precursor ion and contains all of the constituent atoms of that ion as well as additional atoms or molecules. Adduct ions are often formed in a

mass spectrometer Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a '' mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is us ...

ion source.

References

{{Reflist Chemical reactions Solid-state chemistry General chemistry

Adduct ions

See also

References