Combination, Synthesis, or Addition Reactions

Combination or addition reactions involve the addition of a compound B to a compound A (or the addition of a reagent to a substrate) and results in the complete consumption of both compounds (or both reagent and substrate). Therefore, this type of reaction is 100% atom economical and efficient with no generation of waste or by-product. 

These three examples illustrate the different types of combination reactions. 

One element and one compound can combine to form a different compound  

Recall from Chapter 2 the definition of atom economy, the ratio of the mass of the species in the desired product relative to the mass of all of the reactants. In all of these reactions the atoms present in the reactants are also present in the products. In this case it is implied that these reactions are 100% atom economical. Remember from Chapter 2 that atom economy is a mass utilization number only it does not take into account the energy usage, the toxicity of the products, or whether the feedstocks are derived from renewable materials. 

There are two main types of addition reactions, involving either an electrophile or a nucleophile as one of the starting compounds. All addition reactions of organic compounds involve the breaking of a double bond (n bond) and the formation of two new single covalent bonds (o bonds). 

---