During which time periods during the past 800,000 years has the concentration of atmospheric carbon dioxide exceeded our current values of 400 ppm?

2-bromo-2-methylbutane undergoes an e1 elimination reaction in the presence of ethanol. in the next reaction only one of the possible products is represented. although the product shown is not the major product of the reaction, notice that there is more than one way it can be produced. complete the mechanism and draw the missing substances.