Synthesis of 1-bromobutane?
Would refluxing a mixture of 1-buntanol and hydrobromic acid be a good way to sythesize 1-bromobutane?
Answer:
In general, yes, it is possible to use a 47% HBr solution to make 1-bromobutane from n-butanol. The more efficient method to use though is the H2SO4 catalyzed reaction using NaBr, which ultimately is a source of HBr. Using HBr is more efficient for secondary and tertiary alcohols, given that sulfuric acid promotes the undesired side-reactions of dehydration to form an alkene through elimination OR the formation of ethers. Since primary alcohols are more stable towards dehydration, the use of the sulfuric acid catalyst is preferred, since the acid is present in only catalytic amounts. Note that the above comment by Jack is flawed, in that HBr is far more acidic that an -OH group, and would be readily protonated by HBr. The second answer is more correct, although NaBr alone would not react due to an -OH group being a horrible leaving group under these conditions! The Br- nucleophile could not attack the primary carbon.
Another, and likely more efficient method, would be to convert the alcohol to the tosylate using TsCl, followed by the Sn2 reaction using NaBr.
No. Both 1-butanol and HBr are ACIDS. They will only give up their protons, but the OH on butanol will not react with a proton to form water.
Look for O-CHEM help on how to add a bromine to a primary carbon.
We just did this a few weeks ago in Ochem lab. We used NaBr.
If you use HBr, you'll protonate the oxygen, then the Br anion will deprotonate at the 3rd carbon, lone pairs will form a double bond and you'll lose water thru the E2 mechanism to generate 1-butene.
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Answer:
In general, yes, it is possible to use a 47% HBr solution to make 1-bromobutane from n-butanol. The more efficient method to use though is the H2SO4 catalyzed reaction using NaBr, which ultimately is a source of HBr. Using HBr is more efficient for secondary and tertiary alcohols, given that sulfuric acid promotes the undesired side-reactions of dehydration to form an alkene through elimination OR the formation of ethers. Since primary alcohols are more stable towards dehydration, the use of the sulfuric acid catalyst is preferred, since the acid is present in only catalytic amounts. Note that the above comment by Jack is flawed, in that HBr is far more acidic that an -OH group, and would be readily protonated by HBr. The second answer is more correct, although NaBr alone would not react due to an -OH group being a horrible leaving group under these conditions! The Br- nucleophile could not attack the primary carbon.
Another, and likely more efficient method, would be to convert the alcohol to the tosylate using TsCl, followed by the Sn2 reaction using NaBr.
No. Both 1-butanol and HBr are ACIDS. They will only give up their protons, but the OH on butanol will not react with a proton to form water.
Look for O-CHEM help on how to add a bromine to a primary carbon.
We just did this a few weeks ago in Ochem lab. We used NaBr.
If you use HBr, you'll protonate the oxygen, then the Br anion will deprotonate at the 3rd carbon, lone pairs will form a double bond and you'll lose water thru the E2 mechanism to generate 1-butene.
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