How to Understand the Difference in Reactivities between an Alkene and an Alkyne - Part 3

Reactivity of an organic compound depends on several factors, and so does that of an alkene or an alkyne!


An organic reaction takes place depending on multiple parameters including (but not limited to) the substrate(s), reagent(s), solvent(s), catalyst, reaction conditions, viz., temperature, pressure, moisture.

For one, an isolated double bond (alkene) is more reactive than an isolated triple bond (alkyne) toward electrophilic addition (AE) reactions. This means saying an alkene is more reactive than an alkyne does not make sense as the reverse might be the case if the reaction conditions were different.

Conjugated dienes are thermodynamically stable & kinetically unstable; however, methyl substitution on the allylic carbocation increases its stability by hyperconjugation.

Question:

Predict the major product(s) of the following reactions:



Click/tap to enlarge the image

Solution infographic:



Click/tap to enlarge the image

The curious cases of conjugated dienes❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

(1)    Wikipedia Contributors. Electrophilic addition. Wikipedia. https://en.wikipedia.org/wiki/Electrophilic_addition.

‌(2)    Ncert. Chemistry : Textbook for Class XI - Part.II; National Council Of Educational Research And Training: New Delhi.

(3)    Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

(4)    Graham, T. W.; Fryhle, C. B.; Snyder, S. A. Organic Chemistry.; Hoboken, Nj John Wiley Et Sons, Inc, 2016.

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