Dehydration of Alcohol

3 Key excerpts on "Dehydration of Alcohol"

• 

  eBook - PDF

  General, Organic, and Biological Chemistry

  An Integrated Approach

  • Kenneth W. Raymond(Author)
  • 2012(Publication Date)
  • Wiley

    (Publisher)

  When more than one alkene can be formed from a particular alcohol, the major product is the one produced by removal of H from the neighboring carbon atom that carries fewer H atoms. Of the possible 2-butanol dehydration products (1-butene and 2-butene), 2-butene is the major one (Figure 9.6). CH 3 CH 2 CHCHCH 3 ¡ H ± heat CH 3 ¬ CH 3 CH 2 C“CHCH 3 ± H 2 O CH 3 ¬ OH ¬ 3-Methyl-2-pentene 3-Methyl-2-pentanol H¬C¬C¬¬C¬C¬H ¡ H ± heat H ¬ H ¬ H ¬ H ¬ H¬C¬C“C¬C¬H ± H 2 O H ¬ H ¬ H ¬ H ¬ H ¬ H ¬ H ¬ H ¬ H ¬ OH ¬ 2-Butene ¡ H ± heat 1-Methylcyclopentene 2-Methylcyclopentanol H 3 C OH H 3 C 2-Butanol (major product) (major product) (major product) 2 H atoms 3 H atoms ± H 2 O ■ FIGURE 9.6 Dehydration of Alcohols When alcohols are dehydrated in the presence of H + and heat, the major product is that formed by removal of iOH from one carbon atom and removal of iH from the neighboring C atom that carries fewer H atoms. SAMPLE PROBLEM 9.5 Oxidation and Dehydration of Alcohols Draw the organic product expected from each reaction. a. K 2 Cr 2 O 7 CH 3 CH 2 CH 2 OH c. H + heat CH 3 CH 2 CH 2 OH b. K 2 Cr 2 O 7 CH 3 CHCH 3 OH ƒ d. H + heat CH 3 CHCH 3 OH ƒ STRATEGY Begin by checking the reactants or conditions to determine which type of reaction should be expected—two of the reactions involve oxidation and two involve dehydration. Once 344 CHAPTER 9 Organic Reactions 2—Alcohols, Ethers, Aldehydes, and Ketones 9.4 A L D E H Y D E S A N D K E T O N E S Ketones and aldehydes contain a carbonyl (C “ O) group. In a ketone the carbonyl car- bon atom is attached to two other carbon atoms and in an aldehyde it is attached to one carbon atom and one hydrogen atom or to two hydrogen atoms. When naming aldehydes and ketones according to the IUPAC rules, the carbonyl group (C “ O) must be part of the parent chain, which is numbered from the end nearer this group. Since the carbonyl carbon atom of an aldehyde is always in position number 1, its position is not specified in the name.

  Sign up to read

  Learn more about book
• 

  eBook - PDF

  Experimental Organic Chemistry

  A Miniscale & Microscale Approach

  • John Gilbert, Stephen Martin(Authors)
  • 2015(Publication Date)
  • Cengage Learning EMEA

    (Publisher)

  Thus, the ease of Dehydration of Alcohols by the E1 mechanism is in the order 3° > 2° W 1°, paralleling the relative stabilities of carbocations. In the case of primary alcohols, ionization of the oxonium ion 12 would produce a highly unstable 1° carbocation ( 12 , R 3 5 R 4 5 H), so the alternate E2 ( elimination bimolecular ) mechanism of Equation 10.8 applies. + H 2 O + + OH 2 + R H RO: H R 2 R 1 15 13 rds + H OH 2 R 2 R 4 R 3 R 1 12 H OH 2 R 2 R 4 R 3 R 1 R 2 R 1 R 4 R 3 R 4 R 3 12 Transition state + + + + δ + δ + (10.7) OH 2 + H 2 O + R + + CH 2 H H RO: H H R 2 R 1 OH 2 R 2 R 1 12 rds (10.8) As illustrated in Equations 10.6–10.8, each of the steps along the reaction path-way is reversible, so an alkene may undergo acid-catalyzed hydration to form an alcohol. In practice, reversal of the dehydration may be avoided by removing the alkene, whose boiling point is always lower than the parent alcohol, from the Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 344 Experimental Organic Chemistry ■ Gilbert and Martin reaction mixture by distillation. This technique shifts the equilibrium to the right and maximizes the yield of alkene. You may recall that shifting an equilibrium of a reversible reaction to the right by removing one of the products as it is formed fol-lows from the Le Châtelier principle . According to Equation 10.6, elimination and substitution reactions can be com-peting pathways (see also Sec. 14.3), but the relative importance of each may often be controlled through proper choice of reaction conditions and reagents.

  Sign up to read

  Learn more about book
• 

  eBook - ePub

  Chemistry of Dehydrogenation Reactions and Its Applications

  • Syed Shahabuddin, Rama Gaur, Nandini Mukherjee(Authors)
  • 2024(Publication Date)
  • CRC Press

    (Publisher)

  4 Dehydrogenation Reaction of Aliphatic and Aromatic Alcohols

  Vijay Bahadur and Chandni Pathak

  DOI: 10.1201/9781003321934-4

  4.1 OBJECTIVES

  After studying this unit, students should be able to understand the following:

  • Dehydrogenation of alcohols
  • Acceptorless dehydrogenation of alcohols
  • Conversion into different functionality through acceptorless dehydrogenation
  • Acceptorless dehydrogenation of alcohols through a nano-catalyst
  • Acceptorless dehydrogenation of alcohols through a photo-catalyst

  4.2 DEHYDROGENATION REACTION

  Removal of a hydrogen molecule from feedstock is the specific meaning of a dehydrogenation reaction. It is a type of elimination reaction. The major application of dehydrogenation reactions is in the petrochemicals industry, which converts non-reactive alkane into unsaturated hydrocarbon and aromatic compounds. It is a type of endothermic reaction favoured by high temperatures. The dehydrogenation product of aliphatic alcohol will transform into carbonyl compounds, depending on the type of alcohol. This chapter discusses recent progress in the dehydrogenation of alcohols.

  4.3 ALIPHATIC AND AROMATIC ALCOHOLS

  Alchemists referred to alcohols as “spirits of wine” and started to speak of “alcohol of wine” and then simply “alcohol.”

  Organic compounds having hydroxyl (−OH) groups are known as alcohols. Alcohols are very familiar and valuable compounds in nature, industry, and everyday things. The general formula for simple acyclic alcohol is Cn H2n+1 OH, where n=1, 2, 3, etc. Aromatic compounds contain a hydroxy group on a side chain in which the −OH group is attached to a sp3 hybridized carbon atom next to an aromatic ring.

  In allylic and benzylic alcohol, the −OH group is glued to an sp3 hybridized carbon next to the carbon-carbon double bond and aromatic ring. In vinylic alcohol, the −OH group is directly bonded to a carbon-carbon double bond. Allylic and benzylic alcohols may be primary, secondary, or tertiary.

  Sign up to read

  Learn more about book