Friedel-Crafts monoalkylation of 1,3-dimethylbenzene with tert-butyl chloride in the presence of FeCl3 as a catalyst.

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For EACH of the following reactions (a)-(d) provide a curved arrow mechanism and where appropriate briefly comment on any issues of selectivity that arise. (a) (b) (c) CHO MeO OMe 3 OH MeO NH OEt Me (i) Ph3P=CBr2 (ii) "BuLi (2 equivs) (iii) Mel + H₂SO4 (cat) OMe H₂O Me3Si * TfO OMe O MeCN CO₂Me MeO CsF, NaHCO3 Me COMe OMe

(a) In an acid-catalyzed hydration, one of the following 10 carbon alkynes is expected to produce a single hydration product? Select the correct alkyne and draw the structure of the hydration product that is formed from this alkyne. (I) 2-decyne; (II) 3-decyne; (III) 4-decyne; (IV) 5-decyne; (V) none of these will give a single hydration product. (b) The reaction shown below gives Compound X as the major product. The mass spectrum of X is shown. Br2, H20 Compound X 100 - MS-IW-5644 80 60 40 - 20 - 20 40 60 80 100 120 140 160 180 200 220 m/z Considering the reactions of alkynes and the MS data, de duce which of following structures corresponds to X: Br Br HO, IV V I II II Support your answer with a reaction mechanism for fomation of X and identification of relevant peaks in the mass spectrum. 12 Relative Intensity

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(b) Strongly electron-withdrawing substituents on benzene rings are meta-directing. Show by drawing the resonance structures for the various possible intermediates why this is the case using nitrobenzene as an example.

(a) What product would you expect from cleavage of tetrahydrofuran with HI? (b) Outline a mechanism for the reaction.