Addition reactions polar

Several reagents add to double bonds by a two-step polar process. In this section, we will describe examples of this reaction type, after which we will consider details of the reaction mechanism. 

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Problom 6.50 Write structures for the products of the following polar addition reactions ... 

Irradiation of phenyl substituted diacetylenes yields both protonated products and reduction products. The photoreduction products seem to originate from the triplet excited state, since oxygen quenches the photoreduction almost completely. However, oxygen does not quench the polar addition reaction, supporting a singlet excited state mechanism for the formation of type B photoproducts (Cl protonation product). 

Certain advantages have been claimed for polar addition reactions using hydrogen sulphide and boron trifluoride at -70 °C. 

The Chemistry of Vision Addition and Substitution Reactions Compared Polar Addition Reactions Addition of Unsymmetric Reagents to Unsymmetric Alkenes Markovnikov s Rule Mechanism of Electrophilic Addition to Alkenes Markovnikov s Rule Explained Reaction Equilibrium What Makes a Reaction Go ... 

This chapter continues our discussion of addition reactions, and many of the mechanistic ideas of Chapter 9 apply. For example, many polar addition reactions start with the formation of the more stable carbocation.The most important new concept in this chapter is the requirement for overall anti addition introduced by three-membered ring intermediates. This concept appears most obviously in the trans bromination and chlorination of alkenes. 

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