Post-Lab Question #1: Even though this has to do with a lab that you will bedoin
ID: 940888 • Letter: P
Question
Post-Lab Question #1: Even though this has to do with a lab that you will bedoing in the future, it’s appropriate here since it deals with oxidation statesand you learned about Grignard reagents in CHEM231.Consider the formation of a Grignard reagent from an alkyl halide, as shownbelow:CH3CH2CH2Br + Mg ? CH3CH2CH2MgBrDetermine the starting and ending oxidation states of the bolded carbon. Isthat carbon oxidized or reduced? (3 points)Post-Lab Question
#2: Your book says that the reaction that you performedis limited to secondary alcohols since primary alcohols will often overoxidizeto the carboxylic acid. Explain why the reaction will not work on tertiaryalcohols either.
(2 points)Post-Lab Question #3: In introductory chemistry, you were taught aboutcharges, as in the ionic charges in a compound like MgCl2.In many cases, charges and oxidation numbers are similar, if not the same –this is the case for the atoms in MgCl2. That said, for organic molecules,charges and oxidation numbers can be and usually are very different.Explain why atom/ion charges and oxidation number are essentially thesame for MgCl2 while they are very different for something like methane,and the assumptions that are made when discussing each. Be sure tosupport your claims. (4 points)
Post-Lab Question #4: A student that is unfamiliar with organic chemistryattempts the oxidation of 3-methyl-1-pentanol using the method that youused for this lab. If he started with 3.27 g of 3-methyl-1-pentanol andisolated 3.42 g of product of the product whose IR spectrum is shown below,determine the structure of the product and the percent yield?
Explanation / Answer
Soln. #1 : The oxidation state of carbon attached directly to halide is +1 and that to Mg is -1. So the carbon is reduced.
Soln. #2 : Tertiary alcohols does not have any H's attached to the carbon containing the -OH group. The presence of H is essential in the oxidation reaction and hence tertiary alcohols does not undergo this oxidation reaction.
Soln. #3 : In case of organic molecules, hybridization of atomic orbitals occurs to accomodate all the observed bonds formed to a atom. For carbon it would be expected to form only two bonds, however it shows formation of fours identical bonds. In order to form such bonds the 2s electron gets excited to the empty 2p orbital and thus carbon now has a setp of four unpaired electrons in sp3 hybrid orbitals. Thus organic molecules behave differently than inorganic salts.
Soln. #4 : Oxidation of 3-methyl-1-pentanol yields 3-methyl-penatnoic acid.
Theoretical mass of product formed = (3.27 g/102.174 g/mol) x 116.16 g/mol = 3.72 g
Percent yield of reaction = 3.42 x 100/3.72 = 92.0%