Lewis acids are defined as the compounds that have a strong tendency to receive an additional pair of electrons from the Lewis bases and the Lewis bases donate one pair of electrons. This acid base reaction forms an adduct, and adduct is a compound that have a coordinate covalent bond and both the electrons are provided by only one atom. It is very common to find an electron-deficient molecules which have one deficient octet of electron around one atom. These molecules have a tendency to acquire an octet electron configuration, and this is done by reaction with one atom that have a lone pair of electron.
According to the concept of Brønsted–Lowry of acid and bases, a base is defined as any specie that can receive a proton, and acids are any species that can donate protons. The definition proposed by Lewis was an alternative to the previous definition, which focused on pair of electrons. According to Lewis, any species that can donate a pair of electron is known as Lewis base, and any species that can accept a pair of electron is known as Lewis acid. All the Brønsted–Lowry bases, which are proton acceptors, can also donate a pair of electrons. Some examples of the Brønsted–Lowry bases can be: OH−, H2O, and NH3. This proves that the definition that has been given by Lewis is not contradictory to the definition of Brønsted–Lowry of acid and bases. The definition given by Lewis also expands the definition of acids, so that it includes substances other than H+ ion.
Some molecules such as BCl3 are electron deficient molecules, have less than an octet of electrons around one atom and these substances have a strong tendency for gaining of an additional electrons pair and this achieved by reacting with other substance that contain a lone pair of electron. The definition of Lewis is less obstructive than both the Brønsted–Lowry and the Arrhenius definition, which grew out of the observation from him of the tendency. A general Brønsted–Lowry acid-base reaction that is depicted using the Lewis electron symbols is provided below:
H+ + :B →H : B+
Lewis acid Electron pair acceptor + Lewis base electron pair donor
The H+ proton has no valence electrons and can be considered as a Lewis acid because it can accept a lone pair of electron to form a bond. The proton is known to react with bases. For an example, the neutral compounds of boron, aluminium and other element of Group 13, that possess only six valence electrons, and have a very strong affinity for electron pairs. These compounds are potent Lewis acids that react with an electron-pair donor such as ammonia in order to form an acid–base adduct, which is a covalent bond. An example is given below:
BF3 + NH3 →F3B : NH3
Lewis acid + Lewis base→Acid-base adduct
The coordinate covalent bond is also known as dative bond and these type of bonds are formed when electron pairs are shared between two atoms. The attraction of the electron pairs by both the nuclei helps in holding the atoms together. During the formation of a simple covalent bond, one electron is supplied to the bonds by each atom and in the case of coordinate covalent bonds it may not be the case. In the case of co-ordinate covalent bonds, the electron pair comes from one atom only.
An example of Co-ordinate covalent bond
The reaction between ammonia and hydrogen chloride
NH3 + HCl→NH4Cl
The NH4+ are formed due to the transfer of a hydrogen ion from the hydrogen chloride to the lone pair of electrons on the ammonia molecule.
A dative covalent bond is formed by the attachment of the fourth hydrogen in the ammonium ion, NH4+, this because there is a transfer of the hydrogen nucleus from the chlorine to the nitrogen. The electron of the hydrogen is left behind on the chlorine in order to form a negative chloride ion.
How to identity Lewis acids and bases from a chemical reaction
Example 1: BH3 + (CH3)2S → H3B : S(CH3)2
The given things are the reactants and the products.
Solution: In the above given example, in BH3, there are six valence electrons in boron. Thus, in this case it is electron deficient and can accept a pair of electrons. Like the oxygen, the sulfur atom in the compound (CH3)2S has two lone pairs of electrons. So, the (CH3)2S compound is capable of donating on electron pair to the boron atom of BH3. Thus, in this example, the Lewis acid is BH3 and the Lewis base is (CH3)2S.
Example 2: CaO + CO2 → CaCO3
The given are the reactants and the products.
MyAssignmenthelp.com is known for providing high quality dissertation help to students in USA. With an efficient team of writers, we are capable of providing inclusive dissertation writing services in more than 100 subjects. Apart from writing help, we also provide dissertation editing services to those who struggle to review their papers after writing it. Hence, we serve as the best platform for those who struggle to put up a good dissertation.
Just share requirement and get customized Solution.
Our writers make sure that all orders are submitted, prior to the deadline.
Using reliable plagiarism detection software, Turnitin.com.We only provide customized 100 percent original papers.
Feel free to contact our assignment writing services any time via phone, email or live chat. If you are unable to calculate word count online, ask our customer executives.
Our writers can provide you professional writing assistance on any subject at any level.
Our best price guarantee ensures that the features we offer cannot be matched by any of the competitors.
Get all your documents checked for plagiarism or duplicacy with us.
Get different kinds of essays typed in minutes with clicks.
Calculate your semester grades and cumulative GPa with our GPA Calculator.
Balance any chemical equation in minutes just by entering the formula.
Calculate the number of words and number of pages of all your academic documents.
Our Mission Client Satisfaction
An efficient writing assignment service that comes at a reasonable price. It will never let you down. Very satisfied with the service.
Very fast work and really academic. The proffessor not using very professional words in case that will cause some problems with us. The assignment satisfy all the requirement! It\'s cost-effective!
Great service with friendly staff. they prepare good solutions in a fair period of time. recommended.
Thank You very much for the help. You guys are really amazing. Looking forward to working with you soon.