1 The Diels-Alder reaction is a conjugate addition reaction of a conjugated diene to an alkene (the dienophile) to produce a cyclohexene. 2  The simplest example is the reaction of 1,3-butadiene with ethene to form cyclohexene:3  The analogous reaction of 1,3-butadiene with ethyne to form 1,4-cyclohexadiene is also known: Due to the high degree of regio-and stereoselectivity (due to the concerted mechanism), the Diels-Alder reaction is a very powerful reaction and is widely used in synthetic organic chemistry.
Best Answer: Buyers have up 7 days to pay for an item before you as a seller can open an unpaid item case with ebay. They have a whole process they ask that sellers follow: Buyers automatically enter into a legally binding contract to purchase the item from the seller if they win an online auction or use the Buy It Now feature.
I primarily do fixed price listings, and give the buyers 3 days to pay from the time they purchase the item or the time I accept their offer. You can open an unpaid item case after 2 days, and the buyer has 4 more days after that to pay - that will get you the eBay final value fees back. I'm not sure how it would work with a second chance offer, though. To be honest, a second chance offer at this point likely isn't worth it.