Aldehyde Common Names Use the common name of the acid. Drop -ic acid and add -aldehyde. >1 C:formic acid,formaldehyde >2 C's:acetic acid,acetaldehyde >3 C's:propionic acid,propionaldehyde >4 C's:butyric acid,butyraldehyde. => Chapter 18 11
Chapter 18 11 Aldehyde Common Names • Use the common name of the acid. • Drop -ic acid and add -aldehyde. ➢1 C: formic acid, formaldehyde ➢2 C’s: acetic acid, acetaldehyde ➢3 C’s: propionic acid, propionaldehyde ➢4 C’s: butyric acid, butyraldehyde. =>
Boiling Points More polar,so higher boiling point than comparable alkane or ether. Cannot H-bond to each other,so lower boiling point than comparable alcohol. CH,CH,CH,CH3CH3一O一CH,CH butane methoxyethane bp 0C bp 8C CH,CH2-C一H CH,-C-CH,CH,CH,CH,-OH => propanal acetone 1-propanol bp 49C bp 56C bp 97C 12
Chapter 18 12 Boiling Points • More polar, so higher boiling point than comparable alkane or ether. • Cannot H-bond to each other, so lower boiling point than comparable alcohol. =>
Solubility Good solvent for alcohols. Lone pair of electrons on oxygen of carbonyl can accept a hydrogen bond from O-H or N-H. Acetone and acetaldehyde are miscible in water. => Chapter 18 13
Chapter 18 13 Solubility • Good solvent for alcohols. • Lone pair of electrons on oxygen of carbonyl can accept a hydrogen bond from O-H or N-H. • Acetone and acetaldehyde are miscible in water. =>
Formaldehyde Gas at room temperature. Formalin is a 40%aqueous solution. HO OH -_H 0 H一C H formaldehyde, b.p.-21C formalin trioxane,m.p.62C => Chapter 18 14
Chapter 18 14 Formaldehyde • Gas at room temperature. • Formalin is a 40% aqueous solution. O C O C O C H H H H H H heat H C O H H2O H C H OH HO trioxane, m.p. 62C formaldehyde, b.p. -21C formalin =>
2 IR Spectroscopy Very strong C=O stretch around 1710 cm-1. Conjugation lowers frequency. Ring strain raises frequency. Additional C-H stretch for aldehyde:two absorptions at 2710 cm-1 and 2810 cm-1. => Chapter 18 15
Chapter 18 15 IR Spectroscopy • Very strong C=O stretch around 1710 cm-1 . • Conjugation lowers frequency. • Ring strain raises frequency. • Additional C-H stretch for aldehyde: two absorptions at 2710 cm-1 and 2810 cm-1 . =>