Question

Why is $ \text{FeB}{{\text{r}}_{\text{3}}} $ a lewis acid?

Answer 1

Hint: A Lewis acid is a chemical species with an empty orbital that may accept an electron pair from a Lewis base and create a Lewis adduct. The transfer of a pair of electrons from a base to an acid represents a Lewis acid-base reaction. A hydrogen ion absorbs a pair of electrons despite the fact that it has no electrons. Both the Bronsted-Lowry and Lewis classifications classify it as an acid.

Complete Step By Step Answer:
Metal ions like $ \text{N}{{\text{a}}^{\text{+}}}\text{, M}{{\text{g}}^{\text{2+}}}\text{, C}{{\text{e}}^{\text{3+}}} $ are frequently sources of coordinatively unsaturated derivatives that form Lewis adducts when reacting with a Lewis base. Other reactions are simply known as "acid-catalyzed" reactions. Because they may absorb or give a pair of electrons depending on the reaction, certain molecules, such as H2O, can behave as both Lewis acids and Lewis bases.
The chemical compound $ \text{FeB}{{\text{r}}_{\text{3}}} $ stands for iron(III) bromide. This red-brown odourless chemical, also known as ferric bromide, is employed as a Lewis acid catalyst in the halogenation of aromatic compounds. Acidic solutions are formed when it dissolves in water. In organic chemistry, ferric bromide is occasionally employed as an oxidant, for example, in the conversion of alcohols to ketones. It's utilised in the bromination of aromatic compounds as a Lewis acidic catalyst. It is frequently produced in situ for the latter uses.
A Lewis acid, as you undoubtedly know, is a chemical that can receive electron pairs.
When looking at $ \text{FeB}{{\text{r}}_{\text{3}}} $ , the fact that you have a transition metal, Fe, linked to a highly electronegative element, Br, should be the first thing that comes to mind.
The Fe gains a partial positive charge as a result of the difference in electronegativity, allowing it to receive an electron pair. Because transition metals may extend their octets to accommodate additional electrons, it's a reasonable rule of thumb to assume that compounds produced by transition metals and highly electronegative elements will almost always be Lewis acids.
Because of its strong Lewis acid nature, $ \text{FeB}{{\text{r}}_{\text{3}}} $ is employed as a catalyst in the bromination of benzene.
Without getting into too much detail, the bromine ( $ \text{B}{{\text{r}}_{\text{2}}} $ ) molecule interacts with FeBr3 and contributes two electrons. $ \text{B}{{\text{r}}_{\text{2}}} $ becomes more electrophilic as a result of this polarisation (more attracted to electrons).

Note:
Lewis base and Lewis acid are more or less equivalent with the words nucleophile and electrophile. However, these words highlight the kinetic component of reactivity, particularly their abstract noun forms nucleophilicity and electrophilicity, whereas Lewis basicity and Lewis acidity emphasise the thermodynamic aspect of Lewis adduct production.