More recent IUPAC recommendations now suggest the newer term " hydronium " be used in favor of the older accepted term " oxonium " to illustrate reaction mechanisms such as those defined in the Brønsted – Lowry and solvent system definitions more clearly, with the Arrhenius definition serving as a simple general outline of acid – base character.

According to Brønsted – Lowry acid-base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction ; by extension, a base is the substance which receives that hydrogen ion.

* 1879 – Johannes Nicolaus Brønsted, Danish physical chemist ( d. 1947 )

Independently from Johannes Nicolaus Brønsted he has developed the Brønsted – Lowry acid – base theory and was as a founder-member and president ( 1928 – 1930 ) of the Faraday Society.

This led in 1923 to his formulation of the protonic definition of acids and bases, now known as Brønsted – Lowry acid-base theory, independently of the work by Johannes Nicolaus Brønsted.

* Chemistry: Molecular theory — Kinetic theory of gases — Molecular orbital theory — Valence bond theory — Transition state theory — RRKM theory — Chemical graph theory — Flory-Huggins solution theory — Marcus theory — Lewis theory ( successor to Brønsted – Lowry acid – base theory ) — HSAB theory — Debye – Hückel theory — Thermodynamic theory of polymer elasticity — Reptation theory — Polymer field theory — Møller – Plesset perturbation theory — Density Functional Theory — Frontier molecular orbital theory — Polyhedral skeletal electron pair theory — Baeyer strain theory — Quantum theory of atoms in molecules — Collision theory — Ligand field theory ( successor to Crystal field theory ) — Variational Transition State Theory — Benson group increment theory — Specific ion interaction theory

* February 22 – J. N. Brønsted, Danish chemist ( d. 1947 )

Within the Brønsted – Lowry acid-base theory ( protonic ), a conjugate acid is the acid member, HX, of a pair of two compounds that transform into each other by gain or loss of a proton ( hydrogen ion ).

As Brønsted – Lowry bases are proton acceptors, a weak base may also be defined as a chemical base in which protonation is incomplete.

In chemistry, the Brønsted – Lowry theory is an acid-base theory, proposed independently by Johannes Nicolaus Brønsted and Thomas Martin Lowry in 1923.

So the Brønsted – Lowry concept can be defined by the reaction:

A wide range of compounds can be classified in the Brønsted – Lowry framework: mineral acids and derivatives such as sulfonates, phosphonates, etc., carboxylic acids, amines, carbon acids, 1, 3-diketones such as acetylacetone, ethyl acetoacetate, and Meldrum's acid, and many more.

A Lewis base, defined as an electron-pair donor, can act as a Brønsted – Lowry base as the pair of electrons can be donated to a proton.

In 1923 chemists Johannes Nicolaus Brønsted and Thomas Martin Lowry independently recognized that acid-base reactions involve the transfer of a proton.

In 1923, Johannes Nicolaus Brønsted and Martin Lowry published essentially the same theory about how acids and bases behave, using an electrochemical basis.

Brønsted and Lowry generalised this further to a proton exchange reaction:

This means that the Brønsted – Lowry concept is not limited to aqueous solutions.

Some Lewis acids, defined as electron-pair acceptors, also act as Brønsted – Lowry acids.

The aqua ion formed is a weak Brønsted – Lowry acid.

However not all Lewis acids generate Brønsted – Lowry acidity.

but here very few protons are exchanged since the Brønsted – Lowry acidity of the aqua ion is negligible ( K < sub > a </ sub > = 3. 0 × 10 < sup >- 12 </ sup >).

Although zinc chloride solutions are acidic by the Brønsted definition, the zinc cation also specifically attacks hydroxyl groups as a Lewis acid.

The other metal oxides and hydroxides mentioned above also function as Lewis acids rather than Brønsted acids.

Brønsted acids such as HCl, H < sub > 2 </ sub > SO < sub > 4 </ sub >, polyphosphoric acid and p-toluenesulfonic acid have been used successfully.

The reaction can be catalyzed by Brønsted acids and / or by Lewis acids such as boron trifluoride.

Both theories easily describe the first reaction: CH < sub > 3 </ sub > COOH acts as an Arrhenius acid because it acts as a source of H < sub > 3 </ sub > O < sup >+</ sup > when dissolved in water, and it acts as a Brønsted acid by donating a proton to water.

A proton is transferred from an unspecified Brønsted acid to ammonia, a Brønsted base ; alternatively, ammonia acts as a Lewis base and transfers a lone pair of electrons to form a bond with a hydrogen ion.

In this process O < sub > 2 </ sub >< sup >−</ sup > acts as a Brønsted base, initially forming the radical HO < sub > 2 </ sub >·.

The water molecule in turn donates a proton to a second water molecule and, therefore, acts as a Brønsted acid.

A Brønsted-Lowry acid ( or simply Brønsted acid ) is a species that donates a proton to a Brønsted-Lowry base.

The ammonium ion is generated when ammonia, a weak base, reacts with Brønsted acids ( proton donors ):

In this system, Brønsted acids and Brønsted bases are defined, by which an acid is a molecule or ion that is able to lose, or " donate ," a hydrogen cation ( proton, H < sup >+</ sup >), and a base is a species with the ability to gain, or " accept ," a hydrogen cation ( proton ).

Boric acid also exemplifies the usefulness of the Brønsted – Lowry concept for an acid that does not dissociate but does effectively donate a proton to the base, water.

# REDIRECT Brønsted – Lowry acid – base theory

# REDIRECT Brønsted – Lowry acid – base theory

The general reaction scheme is shown below, showcasing the utilization of a Brønsted base as the activating agent as opposed to fluoride, phosphine ligands are also used on the metal center.

Specific and general catalysis is also found in base catalysed reactions and base Brønsted equation also exists with constant β.

Brønsted acid-base reactions are proton transfer reactions while Lewis acid-base reactions are electron pair transfers.

This reaction cannot be described in terms of Brønsted theory because there is no proton transfer.

A second method to prepare fluorescein uses methanesulfonic acid as a Brønsted acid catalyst.

The strongest superacids are prepared by the combination of two components, a strong Lewis acid and a strong Brønsted acid.