CH118K Arenes - The more number of lower level bonds, the...

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Michael Tam Period 10 Bromination of Arenes In this experiment, we determine the relative rates of the free-radical chain reaction of Br with several different arenes. We do this by realizing that the larger number of lower “order” bonds an arene has, the more energy is required to break the C-H bond. Depending on how many carbons the carbon with the hydrogen is attached to, the hydrogen may be classified as primary, secondary, or tertiary; primary means the carbon is bound to 1 other carbon, secondary to 2 others, and tertiary to 3. Additionally, hydrogens may be classified by the hybridization of the carbon to which they are attached. The designations are aliphatic for sp3, vinylic/allylic for sp2(benzylic/aromatic if part of a ring), and acetylinic if bound to a sp-hybridized carbon.
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Unformatted text preview: The more number of lower level bonds, the longer the bromination will take. Additionally, the bromine/arene mixture will turn clear when all the bromine is consumed. Therefore, it is very straightforward to measure the relative reactivities for the arenes. Hydrocarbon A. Toulene 4 minutes 23 seconds Benzylic 1 o B. Methyl cyclohexane 13 minutes Aliphatic 3 o Aliphatic 2 o Aliphatic 1 o C. Ethyl benzene 20seconds Aliphatic 1 o benzylic 2 o Aromatic D. Cyclohexane 52 minutes 9 seconds Aliphatic 2 o E. Control didnt react The data obtained reflected the theory behind the experiment, with the benzylic bonds taking the least time, the greater number of carbons attached the shorter amount of time. The same theory applied to the aliphatics....
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CH118K Arenes - The more number of lower level bonds, the...

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