Hydroboration 반응을 통하여 1-Hexene 에서 anti-markonikov 법칙을 따르는, 즉 less substituted된 반응물인 1-Hexanol 을 합성하여 보고 NMR spectrum과 IR spectrum을 이용하여 확인해 본다.
본 실험은 1-Hexene을 starting material로 하여 hydroboration 과 oxidation 반응을 연속적으로 진행 하여 최종적으로 1-Hexanol을 합성하는 실험이다. 첫 번째 반응인 hydronoration은 borane (BH3)이 THF solvent에서 1-Hexene에 borane addition을 하는 반응으로 1-Hexene과 반응을 하면, 세 1-Hexene 분자가 borane에 연속적으로 addition을 하기 때문에 trihexylborane 이 합성된다.(Eq.2 참조)
이때, Lewis basic 한 solvent (본 실험에서 THF)가 없을 때는 borane이 monomer보다 반응성이 작은 dimer로 이합체를 형성하고 있기 때문에 반응이 일어나지 않는다. 또한 borane의 boron 원자는 electrophilic 하고 steric strain이 적은 form 으로 addition을 하는 것이 더 안정한 화합물을 만들기 때문에 less substituted 탄소 원자인 1번 탄소에 첨가 반응을 하기 때문에 이 반응의 product (trihexylborane) 는 anti-Markovnikov addition product가 된다.
본 실험은 hydroboration-oxidation을통해 1-Hexanol을 합성한다. 이 실험은 물에 민감한 반응을 일으키므로 물을 차단하는 방법을 사용해야 한다.
BH3가 active reagent여서 물과 반응하여 B(OH)3와 dihydrogen gas를 생상해내기 때문이다. 먼저 실험을 하기 전, 실험에 사용되는 도구들을 oven에 건조시켜 물기를 제거해야 한다. solvent역시 dry한 것을 사용한다.
그 다음 실험도구 셋팅시, drying tube( 사용)를 이용해 공기에 있는 습기를 흡수시키도록 한다. stopper역시 물을 차단하는 도구로 사용된다. 더불어 borane을 과량으로 사용해 혹시나 물과 반응한 borane이 생기더라도, 1-hexene과 반응할 수 있는 borane이 남도록 한다.
실험 방법
1. Conducting the Hydroboration of 1-Hexene
1) Wash and rinse the following items with both distilled or deionized waterand acetone, then dry them in a 100 ℃ oven for at least 30 min and vacuum dry: a 25-㎖ 2-neck round-bottom flask, two rubber septa.
2) Prepare an ice-water bath using a 250-㎖ beaker. Using a clean, dry syringe, add 1.7 ㎖ of dry 1-hexene to the round bottom flask through the septum directly over the flask.
3) Cool the flask holding the 1-hexene to 0 ℃ in the ice-water bath.
4) After the reaction flask has been in the ice-water bath for 5 min, use a clean, dry syringe to slowly add 5.0 ㎖ of 1M borane in THF (THF·BF3).
5) Over a 10-min period, add the solution dropwise through the septum to the cold 1-hexene.
6) Once the addition is complete, remove the reaction flask from the ice-water bath.
7) Allow the reaction to warm to room temperature and to remain at room temperature, with occasional swirling, for 30-45 min. After 30-45 min, remove the Claisen adapter.
8) Using a Pasteur pipet, add dropwise approximately 0.4 ㎖ of distilled or deionized water.
2. Oxidizing Trihexyl Borane
1) Add 3 ㎖ of 3M NaOH to the reaction mixture.
2) Working in a fume hood, slowly add 30% as follows : Do not add quickly or the reaction may overheat and explode.
3) Use a Pasteur pipet to add 3 ㎖ of dropwise over a 15-min period. Occasionally, gently swirl the reaction vessel. Add three boiling chips to the reaction flask.
4) Attach a reflux condenser to the reaction flask, as shown in Figure 1. Place the reaction flask so that it barely touches the surface of the sand bath.
5) Alternatively, use a warm-water bath set at 40-50℃ in place of the sand bath. Heat the reaction mixture at 40-50 ℃.
6) Check the temperature by touching a thermometer to the sand alongside the flask.
7) If you use a warm-water bath, maintain the temperature at 40-50 ℃.
8) Allow the reaction to proceed at this temperature for 1hr.
9) Add 3 ㎖ of 3M NaOH to the reaction mixture.
10) Working in a fume hood, slowly add 30% H2O2 as follows : Do not add H2O2 quickly or the reaction may overheat and explode.
11) Use a Pasteur pipet to add 3 ㎖ of 2O2dropwise over a 15-min period. Occasionally, gently swirl the reaction vessel.
12) Add three boiling chips to the reaction flask. Attach a reflux condenser to the reaction flask, as shown in Figure 1.
13) Place the reaction flask so that it barely touches the surface of the sand bath.
14) Alternatively, use a warm-water bath set at 40-50℃ in place of the sand bath. Heat the reaction mixture at 40-50 ℃.
15) Check the temperature by touching a thermometer to the sand alongside the flask.
16)If you use a warm-water bath, maintain the temperature at 40-50 ℃. Allow the reaction to proceed at this temperature for 1hr.
17) After allowing the reaction mixture to cool to room temperature, add 10 ㎖ of diethyl ether. Transfer the mixture to a separatory funnel.
18) Mix by inverting the funnel several times, venting frequently. Drain the bottom aqueous layer back into the original reaction flask.
20) Pour the ether into a 50-㎖ Erlenmeyer flask.
21) Pour the aqueous layer back into the separatory funnel and extract it with two 10-㎖ portions of diethyl ether.
22) Upon the addition of each portion of ether, invert the funnel several times to thoroughly mix the two layers, venting frequently.
23) Separate the two layers as above, combining all the ether extracts in the 50-㎖ Erlenmeyer flask.
24) Place the combined ether extracts back into the separatory funnel.
25) Wash the ether with 7.5 ㎖ of 0.1 M HCl, followed by three 5-㎖ portions of distilled water.
26) For each of the four washes, mix by inverting and venting the funnel several times.
27) After each wash, remove the bottom layer. Retain the bottom layers to discard later. After the last water wash, transfer the ether to a clean 50-㎖ Erlenmeyer flask.
28) Rinse the separatory funnel with 5 ㎖ of ether. Combine this ether rinse with the ether in the Erlenmeyer flask.
3. Removing the Diethyl Ether
A. Using a Rotary Evaporator
Use a rotary evaporator to collect the ether from the product, as directed by your laboratory instructor. Weigh the round-bottom flask after the ether has been removed.
B. Using Distillation
Set up a simple distillation apparatus in the fume hood. Use the 50-㎖ round-bottom flask containing your product as the distilling flask. Use a hot-water bath to distill the ether from the product. Collect the ether in a 50-㎖ beaker. Weigh the round-bottom flask.
4. Purifying the product
1) Assemble the chromatography column with stopcock. Clamp the column to a support stand. Add 2 g of 10% AgNO3on silica gel. Add 0.500 g of anhydrous Na2SO4.
2) Weigh a 50-㎖ Erlenmeyer flask containing two boiling chips. Record the mass. Place this flask under the chromatography column.
3) Dissolve your crude product in 2.5 ㎖ of petroleum ether. Using a Pasteur pipet, transfer this solution to the column, carefully running it down the side of the column in order not to disturb the column packing.
4) Rinse the flask that contained the crude product with 5 ㎖ of 1:4 diethyl ether/petroleum ether.
5) After the original 2.5 ㎖ of solution has soaked into the column packing, add this rinse solution to the column. Allow the rinse to soak into the column packing.
6) Add an additional 20 ㎖ of 1:4 diethyl ether/petroleum ether to the column. Collect all the liquid that drains off the column.
7) When all the liquid has drained through the column, evaporate the ethers in the same manner used in Part 3. Weigh the product and record the mass.
5. Characterizing the Product
A. Using IR Spectroscopy
Place one drop of your product between two salt plates. Obtain an IR spectrum of your product as directed by your laboratory instructor.
B. Using NMR Spectroscopy
Add 5 drops of product to a NMR tube. Dilute with deutero-chloroform. Obtain a NMR spectrum of your product as directed by your laboratory instructor.
C. Using Gas Chromatography
Perform gas chromatography on 5 ㎖ of your product, 2 ㎖ of 1-hexanol, 2 ㎖ of 2-hexanol, and 1 ㎖ of 1-hexene, as directed by your laboratory instructor.
6. Cleaning up
Use the labeled collection containers as directed by your laboratory instructor. Clean your glassware with soap or detergent.
[유기화학실험]Hydroboration and Oxidation of 1-Hexene to Make 1-Hexanol 레포트
1. 실험 이론 및 원리 1.1. 실험 배경 본 실험은 1-Hexene을 starting material로 하여 hydroboration 과 oxidation 반응을 연속적으로 진행 하여 최종적으로 1-Hexanol을 합성하는 실험이다. 첫 번째 반응인 hydronorat
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