Chapter 18

Organic Chemistry

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
aldehydes and ketones easily react to form enols and enolate ions enols have a OH-C=C unit and enolate ions are the same thing minus the proton ( - O-C=C) 18.1 The α Hydrogen and Its pKa carbon adjacent to carbonyl C is alpha next is beta next is gamma no greek letter attached to H attached to carbonyl group alpha protons are relatively acidic (relative to other CH protons) because of inductive and resonance effect O pulls electron density away from bond and resonance stabilizes this positive character enolate ion is conjugate base of aldehyde or ketone major contributor is one with negative charge on O simple aldehydes and ketones of pKa's of about 16-20 close to water (15.7) and similar to alcohols electronegative substituents attached to the alpha carbon make more acidic β-diketones have two carbonyl groups bonded to same C, have pKa of about 9 when aldehydes/ketones present with enolate ions, aldol condensation rxns (next section) take place to form enolate ion completely, use lithium diisopropylamide (LDA-[(CH3)2CH]2NaLi) strong base and too sterically hindered to undergo Nu- addition with carbonyl group 18.2 The Aldol Condensation when carbonyl compound and enolate present, C-C bond formation occurs happens when aldehydes and ketones (with H's of pKa 16-20) treated with strong bases equilibrium to right for aldehydes and left for ketones product called aldol SEE MECHANISM DRAWING ON PAGE 758 aldols undergo dehyration when heated and produce α,β-unsaturated aldehydes have double bond between O=C-C=C conjugation with carbonyl double bond stabilizes the newly formed double bond
Background image of page 1

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

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 04/07/2008.

Page1 / 4

Chapter 18 - aldehydes and ketones easily react to form...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online