Curly arrows fish-hook

The weak Br-Br bond breaks to form two bromine radicals. This can be represented by two single-headed curly arrows, fish hooks, to indicate that only one electron is moving. This is virtually all you will see of this special type of curly arrow until we consider the reactions of radicals in more detail (Chapter 39). When you meet a new reaction you should assume that it is an ionic reaction and use two-electron arrows unless you have a good reason to suppose otherwise. 

Further symbols are used to indieate reaction mechanisms, in particular the use of curly arrows (to represent the movement of pairs of electrons) and fish-hooks (to represent the movement of single eleetrons). Students need to understand the precise meaning of these arrows (whieh electrons move, and where from and where to) to appreeiate how they represent stages in reaetion mechanisms. Students who have been taught the formalism are not neeessarily able to identify the outcome of... 

When we made the allyl cation from allyl bromide, the bromine atom left as bromide ion taking both the electrons from the C-Br bond with it—the C-Br bond broke heterolytically. What if the bond broke homolytically—that is, carbon and bromine each had one electron A bromine atom and an allyl radical (remember a radical has an unpaired electron) would be formed, This reaction can be shown using the singleheaded fish hook curly arrows from Chapter 5 normal double-headed arrows show the movement of two electrons single-headed arrows show the movement of one. 

Curly arrows can be used to represent bond cleavage. A double-headed arrow represents the movement of two electrons (and is used in polar reaction mechanisms). A single-headed arrow (or fish-hook) is used to represent the movement of... 

Notice the use of single-headed (fish-hook) curly arrows (Section 4.1)... 

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