Chapter 22_Class Notes - Chapter 22 Carbonyl...

Info icon This preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 22: Carbonyl Alpha-Substitution Reactions The chemistry of carbonyl compounds can be explained by 4 main reaction types: 1. Nucleophilic Addition Reactions – (Family A) -Aldehydes & Ketones 2. Nucleophilic Acyl Substitution Reactions – (Family B) 3. α -Substitution Reactions (Chapter 22) 4. Carbonyl Condensation Reactions (Chapter 23 - ) Carbonyl Alpha-Substitution Reactions The α -substitution reaction occurs at the α -position The α -substitution of carbonyl compounds occurs via one of two intermediates 1. Enol intermediate or 2. Enolate intermediate ° The enol and enolate are electron rich intermediates that can react with electrophiles 1
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
General Mechanism O H 2
Image of page 2
ENOLS Keto-enol tautomerization – the rapid interconversion between two substances involving the transfer of a proton ° The individual isomers are called tautomers which differ in the position of a double bond and a proton (they are constitutional isomers ) The mechanism of keto-enol tautomerization can either be 1. Acid-catalyzed or 2. Base-catalyzed ( HW - see fig. 22.1, pg 872, McMurry 8 th Ed.) Mechanism: Acid-catalyzed keto-enol tautomerization 3
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Note that Only hydrogens on the α -position of a carbonyl compound are acidic Hydrogens at β , γ , δ etc are not acidic and cannot be removed by base! Why? ° This unique behavior of α -hydrogens is due to the fact that the resultant enolate ion is stabilized by a resonance form that places the charge on the electronegative oxygen 4 Reactions of Enols α -Substitution Reaction: α -halogenation of aldehydes and ketones ° Common α -substitutions in the lab use Cl 2 , Br 2 or I 2 in acidic conditions ° The most common reagent is Br 2 (bromine) in acetic acid
Image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern