Question

6. (a) 3-Butene-2-one can conceivably react as a Lewis acid at any of the three sp2-hybridized carbon atoms. Draw the products of the three Lewis acid-base reactions where each carbon reacts with a general nucleophile, Nuc:-, as well as the arrow-pushing mechanism of the formation of each product. Include resonance structures where required. (11 points) a b c (b) One of the three labeled carbons is much less electrophilic than the other two. Which one, and why? (2 points) (c) Which reaction is the most favorable, and why? That is, which carbon is the most electrophilic? (Assume the reaction which makes the most stable product is most favorable.) (2 points) (d) In strong acid, 3-buten-2-one is protonated on an oxygen lone pair. Draw all resonance structures for this conjugate acid (with curved arrows), as well as a hybrid with appropriately sized partial charges. (5 points) (e) Using any of the RS’s you drew in (d), draw two different possible Lewis acid/base reactions with Nuc:-. Show arrows for the mechanism and structure of the product of each reaction. (4 points)

          6. (a) 3-Butene-2-one can conceivably react as a Lewis acid at any of the three sp2-hybridized carbon atoms. Draw the products of the three Lewis acid-base reactions where each carbon reacts with a general nucleophile, Nuc:-, as well as the arrow-pushing mechanism of the formation of each product. Include resonance structures where required. (11 points)

a

b

c

(b) One of the three labeled carbons is much less electrophilic than the other two. Which one, and why? (2 points)

(c) Which reaction is the most favorable, and why? That is, which carbon is the most electrophilic? (Assume the reaction which makes the most stable product is most favorable.) (2 points)

(d) In strong acid, 3-buten-2-one is protonated on an oxygen lone pair. Draw all resonance structures for this conjugate acid (with curved arrows), as well as a hybrid with appropriately sized partial charges. (5 points)

(e) Using any of the RS’s you drew in (d), draw two different possible Lewis acid/base reactions with Nuc:-. Show arrows for the mechanism and structure of the product of each reaction. (4 points)

6. (a) 3-Butene-2-one can conceivably react as a Lewis acid at any of the three sp2-hybridized carbon atoms. Draw the products of the three Lewis acid-base reactions where each carbon reacts with a general nucleophile, Nuc:-, as well as the arrow-pushing mechanism of the formation of each product. Include resonance structures where required. (11 points)

a

b

c

(b) One of the three labeled carbons is much less electrophilic than the other two. Which one, and why? (2 points)

(c) Which reaction is the most favorable, and why? That is, which carbon is the most electrophilic? (Assume the reaction which makes the most stable product is most favorable.) (2 points)

(d) In strong acid, 3-buten-2-one is protonated on an oxygen lone pair. Draw all resonance structures for this conjugate acid (with curved arrows), as well as a hybrid with appropriately sized partial charges. (5 points)

(e) Using any of the RS’s you drew in (d), draw two different possible Lewis acid/base reactions with Nuc:-. Show arrows for the mechanism and structure of the product of each reaction. (4 points)

Added by Thomas A.

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