Participation by neighbouring groups in addition reactions. Part III. Bromination in acetic acid and trifluoroacetic acid solvents
- 1 January 1975
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 5,p. 503-506
- https://doi.org/10.1039/p29750000503
Abstract
Rate measurements and product analyses for bromination of CH2 CH[CH2]nOH (for n= 1–4) in acetic acid indicated substantial participation by the neighbouring hydroxy-group for n= 3 and a smaller but still significant participation for n= 4. The general pattern of behaviour was very similar to that observed previously for reactions in methanol and water solvents. However, in trifluoroacetic acid solvent the extent of such hydroxy-participation was drastically reduced (three being only 4% ring-closed product for n= 3). The effect is attributed to hydrogen-bonding between the solvent and the hydroxy-substituent, which reduces the nucleophilicity (and hence its effectiveness as a neighbouring group) of the hydroxy-substituent. As for the methanol reactions, there was no kinetic indication of any participation by neighbouring bromine in the bromination of CH2 CH[CH2]nBr in either acetic acid or trifluoroacetic acid solvent.Keywords
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