General Safety Considerations
1. 1-Butanol and 1-bromobutane are toxic and irritating. Avoid all contact by constantly wearing goggles, gloves and working in the hood. Neither of these compounds can be poured down the drain. Like all products, 1-bromobutane should be turned in to your TA in a labeled vial. Any excess butanol should be discarded in non-halogenated waste. 2. H2SO4 is extremely corrosive. In very diluted form it can be poured down the drain, all other precautions described for butanol apply.
3. NaOH solution is corrosive. Handle it like H2SO4.
4. Methylene chloride is toxic and can be extremely irritating to your skin, especially when you are wearing gloves and it goes through them. It is not a bad idea to wear several pairs of gloves while working with it in addition to wearing goggles and working in the hood. 5. If you come in contact with any of the above mentioned chemicals, flush the exposed area for at least fifteen minutes with cold water. In the event of a major spill, consult your instructor.
Chemistry 211-212Preparative Experiments
Chemistry 211-212Investigative Experiments
Name| TA Name:|
Experiment # 7| Lab Day:|
Section 1 (Pre-lab Sections I-VI)| (20 points)|
Section 2 (Results Sections VII - IX)| (60 points)|
Section 3 (Post-lab questions Section X)| (50 points)|
Quality of results| (20 points)|
TOTAL| (170 points)|
SCORE| (percent) ,|
Please note that this lab will have a form write-up. You will be using a form to help you adjust to the changes in format involved in a preparative write-up. This means that your lab report will consist of this cover and the completed form that is found later in this section of the lab book.
You might also want to note that this is a two week experiment. While it is to your advantage to get as much of it done as possible during the first week, the prelab pages of the form will not be collected until the second week of the lab.
Please fill this page out and attach it to the pre-lab form pages when you are ready to submit them for grading. 7-2
SN2 vs E2 vs SN1 vs El
BestMechanismRate LawNucleophile/BaseSubstrate(s)Leaving GroupStereochem| Solvent| Temp| SN2Rate = k[Sub] [Nu]Strong Nucleophile10(20-someGood (weak base)Usually InversionSN2 + E2)*Backside AttackfavoredStereospecific| PolarAprotic| lowertemp| SN1**Rate = k[Sub]Weak Nucleophile3°, allylicGood (weak base)Racemization orbenzylic (2°Partial Racemizationless reactive butNot stereospecificalso possible)| PolarProtic| lowertemps| E2Rate = k[Sub][Nu]Strong Base including3°(2°-someGood (weak base)Anti periplanarBulky BaseE2 + SN2)*transition statepreferredstereospecific| PolarAprotic| highertemps| E1**Rate = k[Sub]Weak Base3°, allylicGood (weak base)Expect bothbenzylic (2°Cis and transless reactive butproductspossible)Not stereospecific| polarProtic| highertemps|
* 2° substrates are a gray area. With strong bases/nucleophile a mixture of SN2/E2 products will form. With a bulky base and/or higher temperatures, E2 products will dominate.
** SN1 and El compete with each other all the time so both products will form to a significant extent. Higher temperatures will favor El products, however.7-4
Nucleophilic Substitution: Preparation of 1-Bromobutane
The theory to support this lab can be found in chapters 9 and 10 of your textbook (Loundon). In this preparative experiment, you will synthesize 1-bromobutane from butanol and hydrobromic acid as outlined in the following equation.
The formation of the major product, 1 bromobutane, can be explained by the following sequence of steps. H2SO4 + H2O →H30+ + HSO4
H30+ + Br→ HBr + H2O
When you carry out the reaction , you will notice two layers in the reaction pot. The lower layer is aqueous and the upper layer is organic. It...