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nucleophile

Having major struggles with this assignment question....

Draw and explain the mechanism for the formation of 1-bromopentane from pentan-1-ol. Explain why this is a nucleophilic substitution reaction.

I've spent a fair few hours on this and finally accepting I need help! xxx
Original post by steveydzy
Having major struggles with this assignment question....

Draw and explain the mechanism for the formation of 1-bromopentane from pentan-1-ol. Explain why this is a nucleophilic substitution reaction.

I've spent a fair few hours on this and finally accepting I need help! x

Bromide ion Br- is a nucleophile, attracted to the partial positive charge on the Carbon atom on pentan-1-ol. The C-O bond breaks, losing the -OH group. Br- is substituted in its place.
Original post by steveydzy
Having major struggles with this assignment question....

Draw and explain the mechanism for the formation of 1-bromopentane from pentan-1-ol. Explain why this is a nucleophilic substitution reaction.

I've spent a fair few hours on this and finally accepting I need help! xxx

Hydrogen bromide (HBr) is used for that reaction. When it reacts with pentan-1-ol, the hydrogen bromide breaks in two heterogenous ionic charges, Br- (negative) and H+ (positive). At the same time the OH-group breaks on the C-Atom, so this atom gets positive charged for short and thus becomes a nucleus.

The negative Br- ion gets attracted that positive C-atom (Br- ion is called nucleophile for that reason!) and this process is known as nucleophilic reaction.

Last but not least the negative OH- and positive H+ forms water as side product. In total the OH-group was substituted by a bromide ion.
(edited 1 year ago)
Reply 4
IMG_7879.jpgI did a level chemistry a few years ago so I believe this reaction mechanism should be sufficient. The marking criteria is usually to demonstrate a curly arrow as the movement of an electron pair, and to include the dipoles on each of the reactants / intermediary steps. The comments left by the user above should be able to explain each step of the reaction process, remember a nucleophile means an electron pair donor.

Edit: if you draw the whole compound it should be H3C H2C H2C H2C as opposed to CH3 CH2 CH2 CH2 (as I have not done) as the bond needs to show coming from the carbon not the hydrogen.
(edited 1 year ago)

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