The reactivity of a bond or atom towards a particular reactant in a compound is significantly influenced by the availability of electrons. The influence on the availability of electron density is influenced by the following factors: inductive effect, mesomeric effect, electromeric effect and hyperconjugation. Inductive Effect In chemical composition and science, the inductive effect is an experimentally observable impact of charge transmission through a chain of atoms in a molecule. It can also be defined as the process of moving electrons along the chain of carbon atoms. It is a permanent effect and results from the presence of a polar covalent bond at one end of the chain and does not depend on the presence of a reagent. Electrons moved towards a more electronegative atom. When the atom or group of atoms has a greater electron-attracting ability than hydrogen, this is the inductive electron-attracting effect, also known as the -I effect. The positive charge is passed on to the other atoms in the chain, if the electronegative atom joins a chain of carbon atoms. Example of inductive effect of electron attraction (-I) effect• NO2> CN>COOH>F>Cl> Br> I > OH> OCH3 > C6H5 > HWhen atoms or groups of atoms have an electron attraction power lower than that of hydrogen, repel the electrons towards the carbon atom this is the inductive effect of electron repulsion, also known as the +I effect. Example of inductive effect of repulsion of electrons (+I).• (CH3)3C > (CH3)2CH > CH3CH2 > CH3The more electronegative atom has a slight negative charge (δ–) and the other atom has a slight positive charge (δ +). Able to decide the point of attachment in the molecule, inductive effects change the electron density in a molecule. Mesomeric effect The mesomeric effect...... in the center of the paper ...... by increasing the length of the bond, the resonance influences the length of the bond: the single bond shortens while the double bond lengthens while the tautomerism has no effect on bond length. Regarding dynamic equilibrium, the resonant structures are not in dynamic equilibrium but the tautomerism is in dynamic equilibrium with each other. The two tautomeric forms exist together although the equilibrium can shift to one side or the other with a change in condition. Tautomers have a physical reality while resonance structures are imaginary. The change in the position of the atom (generally hydrogen) implies tautomerism, while resonance implies only a change in the position of the unshared or pi bond. Example, considering an amide which is 1.52 the resonance shape 1.53 shows a different in the position of the charge, while the tautomer 1.54 shows a different in the position of a hydrogen atom.