Atom economy is a measure of the efficiency of a chemical reaction in terms of the amount of starting materials that are converted into the desired product. It is calculated as the ratio of the molecular weight of the desired product to the total molecular weight of all the reactants.

The goal of atom economy is to maximize the amount of starting materials that are converted into the desired product, minimize the amount of waste that is produced, and reduce the energy consumption of a chemical reaction.

Atom economy is affected by a number of factors, including the type of reaction, the reaction conditions, and the catalyst used.

Atom economy can be improved by using more efficient catalysts, milder reaction conditions, and more selective reagents.

The Diels-Alder reaction, the Heck reaction, and the Suzuki reaction are all examples of reactions with high atom economy.

The combustion of hydrocarbons, the hydrolysis of esters, and the Friedel-Crafts reaction are all examples of reactions with low atom economy.

Atom economy is important because it helps to reduce waste, reduce energy consumption, and reduce the environmental impact of chemical reactions.

Atom economy is calculated by dividing the molecular weight of the desired product by the total molecular weight of all the reactants.

A good atom economy is greater than 90%.

A poor atom economy is less than 50%.

The atom economy of the reaction is calculated as follows: $$Atom economy = rac{Molecular weight of CH_3CH_2Cl}{Molecular weight of CH_3CH_2OH + HCl} = rac{64.5}{46.0 + 36.5} = 0.636$$ Therefore, the atom economy of the reaction is 63.6%.

The atom economy of the reaction is calculated as follows: $$Atom economy = rac{Molecular weight of C_6H_6Cl_6}{Molecular weight of C_6H_6 + 3Cl_2} = rac{290.8}{78.1 + 213.0} = 0.182$$ Therefore, the atom economy of the reaction is 18.2%.

The atom economy of the reaction is calculated as follows: $$Atom economy = rac{Molecular weight of 4CO_2 + 6H_2O}{Molecular weight of 2C_2H_5OH + 3O_2} = rac{176.0 + 108.0}{92.1 + 96.0} = 0.909$$ Therefore, the atom economy of the reaction is 90.9%.

The atom economy of the reaction is calculated as follows: $$Atom economy = rac{Molecular weight of CO_2 + 2H_2O}{Molecular weight of CH_4 + 2O_2} = rac{44.0 + 36.0}{16.0 + 64.0} = 0.333$$ Therefore, the atom economy of the reaction is 33.3%.

The atom economy of the reaction is calculated as follows: $$Atom economy = rac{Molecular weight of 12CO_2 + 6H_2O}{Molecular weight of 2C_6H_5CH_3 + 3O_2} = rac{528.0 + 108.0}{182.2 + 96.0} = 0.778$$ Therefore, the atom economy of the reaction is 77.8%.