Formal Charges
Formal charges have an important role in organic chemistry since this concept helps us to know whether an atom in a molecule is neutral/bears a positive or negative charge. Even if some molecules are neutral, the atoms within that molecule need not be neutral atoms.
Polarity Of Water
In simple chemical terms, polarity refers to the separation of charges in a chemical species leading into formation of two polar ends which are positively charged end and negatively charged end. Polarity in any molecule occurs due to the differences in the electronegativities of the bonded atoms. Water, as we all know has two hydrogen atoms bonded to an oxygen atom. As oxygen is more electronegative than hydrogen thus, there exists polarity in the bonds which is why water is known as a polar solvent.
Valence Bond Theory Vbt
Valence bond theory (VBT) in simple terms explains how individual atomic orbitals with an unpaired electron each, come close to each other and overlap to form a molecular orbital giving a covalent bond. It gives a quantum mechanical approach to the formation of covalent bonds with the help of wavefunctions using attractive and repulsive energies when two atoms are brought from infinity to their internuclear distance.
Acetyl salicylic acid (aspirin), the most widely used medi-cine in the world, has the Lewisstructure at right. (a) What is the hybridization of each C and each O atom? (b) How many localized π bonds are present? (c) How many C atoms have a trigonal planar shape around them? A tetra hedral shape?
Hybridization: This is the intermixing of atomic orbitals to form new hybrid orbitals. This can be used to predict the shape of polyatomic molecules. Tn a carbon compound, the hybridization can be determined from the number of sigma bond involved and from the number of lone pair of an electron from the lewis structure.
Lewis Structure: This is also called an electron-dot structure. This is drawn from the molecular formula of the compound. Its gives an idea about the chemical bonding in a molecule, the number of single bonds or double bonds, the number of lone pair of atoms present, etc. Here, the valence electrons are denoted along with the element. The least electronegative atom is considered as the central atom.
The Lewis structure for Acetyl salicylic acid (aspirin) is,
- Here, the carbons, C1 ,C2 ,C3, C4, C5, and C6, have 3 sigma bonds, 2 C-C sigma bond,s and 1 C-H sigma bond, so, the hybridization of C1 ,C2 ,C3, C4, C5, and C6 is sp2. Its, geometry is trigonal planar geometry.
- In C7 and C8 also, carbons have 3 sigma bonds, 1 C-C sigma bond and 2 C-O sigma bond, so, the hybridization of C7 and C8 is sp2. Its, geometry is trigonal planar geometry.
- In C9, 4 sigma bonds are present, 1 C-C sigma bond,s and 3 C-H sigma bond, so,C9 is sp3 hybridized. Its, geometry is tetrahedral geometry.
- In the oxygen, O1 , it has two sigma bonds, 2 C-O sigma bond and two pairs of lone pair of electron, so, it is sp3 hybridized.
- In O3 and O2, it has one sigma bond and two lone pair of electrons are present, so, it is sp2 hybridized.
- In O4, it has it has two sigma bonds, 1 C-O sigma bond and 1 O-H sigma bond, and two pairs of lone pair of electron, so, it is sp3 hybridized.
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