9_carbonyl

9_carbonyl - Aldehydes and Ketones: The carbonyl group The...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Sec. 9 -Carbonyl Compounds 1 Aldehydes and Ketones: The carbonyl group The carbonyl group contains a short, strong and very polar bond The hybridization of the C and O atoms of the carbonyl group are sp 2 hybridized. The C and O of the carbonyl and the two atoms attached to the carbon all lie in the same plane. The bond angles about the carbonyl are about 120 o . The π bond of the carbonyl is made of the remaining p orbital on the carbon and a similar p orbital on the oxygen. acetaldehyde
Background image of page 1

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

View Full DocumentRight Arrow Icon
Sec. 9 -Carbonyl Compounds 2 + PCC CH 2 Cl 2 OH 1) O 3 , CH 2 Cl 2 , -78°C 2) Zn/HOAc K 2 Cr 2 O 7 , H 2 SO 4 , H 2 O K 2 Cr 2 O 7 , H 2 SO 4 , H 2 O O O H O OH A) B) C) H 2 SO 4 , H 2 O, HgSO 4 OH OH 1. Dicyclohexylborane 1. H 2 O 2 , HO¯ What is the major product formed in each reaction? 1) O 3 , CH 2 Cl 2 , -78°C 2) Zn/HOAc We did not do Friedel-Crafts Alkanoylation (pg 775) Will learn in Chem 267
Background image of page 2
Sec. 9 -Carbonyl Compounds 3 Reactivity of the Carbonyl Group: Mechanisms of Addition There are three regions of reactivity in aldehydes and ketones. The carbonyl group undergoes ionic additions. Polar reagents add to the dipolar carbonyl group according to Coulomb’s law and the fundamentals of Lewis acid-Lewis base interactions. Nucleophiles bond to the carbonyl carbon and electrophiles bond to the carbonyl oxygen.
Background image of page 3

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

View Full DocumentRight Arrow Icon
Sec. 9 -Carbonyl Compounds 4 The following reagents are strong bases and their reactions are irreversible. NaBH 4 and LiAlH 4 reduce carbonyl groups but not carbon-carbon double bonds:
Background image of page 4
Sec. 9 -Carbonyl Compounds 5 Less basic nucleophiles, such as water, alcohols, thiols and amines are not strongly exothermic and establish equilibria that can be pushed in either direction depending upon reaction conditions. Addition of strongly basic nucleophiles typically follow the nucleophilic addition- protonation pathway. Relatively weak nucleophiles are more suitable for the electrophilic protonation- addition mechanism.
Background image of page 5

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

View Full DocumentRight Arrow Icon
Sec. 9 -Carbonyl Compounds 6 Addition of Water to Form Hydrates Water hydrates the carbonyl group. The addition of water to an aldehyde or ketone is catalyzed by either acid or base. The equilibrium reaction forms geminal diols, also called carbonyl hydrates:
Background image of page 6
Sec. 9 -Carbonyl Compounds 7 Hydration is reversible From what you have learnt about the mechanism from the previous slide, order the reactivity of the following compounds from most reactive to least reactive towards hydration Cl 3 C H O O H O H O H 1) 2) 3) 4) A) 1 > 2 > 3 > 4 B) 3 > 2 > 4 > 1 C) 2 > 3 > 4 >1 D) 1 > 4 > 3 > 2 E) 4 > 3 > 1 > 2 K > 10 4 K > 10 3 K ~ 1 K > 10 -2 Equilibrium constant
Background image of page 7

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

View Full DocumentRight Arrow Icon
8 The thermodynamic effects are paralleled by kinetic reactivity Although hydration is favorable in certain cases, it is usually impossible to isolate carbonyl hydrates as pure substances. Carbonyl hydrates play a role as intermediates in subsequent chemistry, such as
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 57

9_carbonyl - Aldehydes and Ketones: The carbonyl group The...

This preview shows document pages 1 - 9. Sign up to view the full document.

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