MediumChemistryHigh School (11–12)Organic Compounds with Functional Groups › Haloalkanes and HaloarenesNumerical
Chlorobenzene, 11.25 g (molar mass 112.5 g/mol), is nitrated with a mixture of concentrated nitric…
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Chlorobenzene, (molar mass ), is nitrated with a mixture of concentrated nitric and sulphuric acids. The overall yield of mononitro products is . Of these, textbook data give ortho, meta and para. Both nitrochlorobenzenes have a molar mass of . Compare the reactivity of one para position with one ortho position, given that there are two ortho positions and one para position. Find the mass of the para product and the mass of the ortho product.
Need a reminder? The key ideaShow
A halogen deactivates the ring but directs to the ortho and para positions. There are two ortho positions, two meta positions and one para position, so the reactivity of one position is its share divided by the number of positions of that kind. The Wurtz-Fittig and Fittig reactions couple halides at random with sodium. A Grignard reagent takes a proton from any O-H or N-H bond and gives an alkane.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. One position. Ortho: . Para: . The ratio is .
Step 2. Mononitro products. of chlorobenzene. At : of nitro products.
Step 3. Para. .
Step 4. Ortho. .
Answer: a para position is times as reactive as an ortho position. The mass of the para product is and of the ortho product .
Check. Statistically ortho would win, . The para product wins because the chlorine atom blocks the ortho positions in part.
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