Acids and Bases: The Bronsted–Lowry Definition 

Perhaps the most important of all concepts related to electronegativity and polarity is that of acidity and basicity. We’ll soon see, in fact, that the acid– base behavior of organic molecules explains much of their chemistry. You may recall from a course in general chemistry that two definitions of acidity are frequently used: the Brønsted–Lowry definition and the Lewis definition.

    A Brønsted–Lowry acid is a substance that donates a hydrogen ion, H⁺,and a Brønsted–Lowry base is a substance that accepts a hydrogen ion. (The name proton is often used as a synonym for H⁺ because loss of the valence electron from a neutral hydrogen atom leaves only the hydrogen nucleus—aproton.) When gaseous hydrogen chloride dissolves in water, for example, a polar HCl molecule acts as an acid and donates a proton, while a water molecule acts as a base and accepts the proton, yielding chloride ion (Cl₂) and hydronium ion (H₃O⁺). This and other acid–base reactions are reversible, so we’ll write them with double, forward-and-backward arrows.

  Chloride ion, the product that results when the acid HCl loses a proton, is called the conjugate base of the acid, and hydronium ion, the product that results when the base H₂O gains a proton, is called the conjugate acid of the base. Other common mineral acids such as H₂SO₄ and HNO₃ behave similarly, as do organic acids such as acetic acid, CH₃CO₂H. In a general sense,

Notice that water can act either as an acid or as a base, depending on the circumstances. In its reaction with HCl, water is a base that accepts a proton to give the hydronium ion, H₃O⁺. In its reaction with ammonia (NH₃), however, water is an acid that donates a proton to give ammonium ion (NH₄⁺) and hydroxide ion, HO^-.

مواضيع ذات صلة

مركبات الآزو متجانسة الحلقة Homocyclic azo compounds

تصنيف مركبات الآزو Classification of azo compound

أصباغ الآزو Azo Dye

تفاعلات الازدواج Reaction Coupling

أملاح الدايازونيوم الاروماتية      Aromtic Diazonium Salt    

أهمية الكواشف العضوية reagents Importance of organic

الثايوزبينات Thiazepines

الدايازبينات Diazepines

الاوكسازبينات Oxazepines

المركبات الحلقية غير المتجانسة Heterocyclic Compounds

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