-1 sigma bond formed by overlap of sp2 orbitals

-1 pi bond formed by overlap of parallel 2p orbitals

-Ex. slides (16-3)

-carbonyl bonded to H atom and C atom

-Exs. slides (16-4)

-Parent chain=longest chain that contains C=O group

-change suffix from -e to -al

-for unsaturated aldehyde change infix from -an to -en

*location of suffix determines numbering pattern

-for cyclic molecules where -CHO is bonded to the ring, add suffix -carbaldehyde

-IUPAC naming retains common names benzaldehyde, cinnamaldehyde, formaldehyde, and acetaldehyde

-Exs. slides (16-6) 

-Parent alkane is the longest chain containing C=O

-Indicate ketone by changing suffic -e to -one

-# chain to give C=O the smaller #

-IUPAC retains common names acetone, acetophenone, and benzophenone

-Exs. slides (16-7)

Naming: Order of precedence

-For compounds containing more than one functional group indicated by a suffix

Func. grp  Suffix (high priority)  Prefix (low priority) 

  Carboxyl      -oic acid                                              

Aldehyde      -al                            oxo-                 

Ketone        -one                          oxo-                 

Alcohol         -ol                        hydroxy-                  Amino         -amine                    amino-                

Sulfhydryl     -thiol                    mercapto-               

*Exs. slides (16-8)

-aldehyde: derived from common name of corresponding carboxylic acid

-ketone: name the 2 alkyl or aryl groups bonded to the carbonyl C and add the word ketone

-Exs. slides (16-9)

-O is more electronegative than C, so C=O is polar

-Aldehydes and ketones=polar and interact in pure state by dipole-dipole interaction

-Have higher bps and are more soluble in H2O than nonpolar compounds of comparable MW

-1 of most common themes of C=O is addition of Nu to form tetrahedral carbonyl addition compound

-Ex. slides (16-11)

-Reaction w/ proton/other Lewis acid to form resonance stabilized cation

*Protonation increases electron deficiency of carbonyl C and makes it more reactive toward Nus

-Ex. slides (16-12)

-Often tetrahedral product of addition to carbonyl group is new chiral center

-If none of starting material is chiral and rxn takes place in achiral environment, then enantiomers formed as racemic mixture

-Ex. slides (16-13)

-1 of most imp. types of Nu additions to C=O group

-New C-C bond formed in process

-4 types of C Nus:

1. RMgX (Grignard)

2. RLi (organolithium)

3. RC-=C'- (alkyne anion)

4. -'C-=N' (cyanide ion)

-Given difference in electronegativity btwn C and Mg (2.5-1.2), C-Mg bond=polar covalent--> Cs- and Mgs+

-In its reactions, Grignard behaves as carbanion

-Anion where C has unshared pair of electrons and bears negative charge

-Good Nu and adds readily to carbonyl group of aldehydes and ketones

-Addition of Grignard to formaldehyde followed by treatment w/ H3O+ gives 1' alcohol

*Slides (16-16)

-Addition to any other RCHO gives 2' alcohol

*Slides (16-17)

-Addition to ketone gives 3' alcohol

*Slides (16-18)

-Generally more reactive in C=O addition rxns than RMgX and typically have higher yields

-Ex. slides (16-20)

-Addition of alkyne anion followed by treatment w/ H3O+ gives alpha-acetylenic alcohol

-Ex. slides (16-21)

-Molecule containing -OH group and -CN group bonded to same C

-Ex. slides (16-23)

Step 1: Nucleophilic addition of cyanide to carbonyl C

Step 2: Proton transfer from HCN gives cyanohydrin and regenerates cyanide ion nucleophile

-Ex. slides (16-24)

-Acid catalyzed dehydration of alcohol gives alkene

-Catalytic reduction fo cyano group gives 1' amine

-Exs. slides (16-25)

-Versatile synthetic method for synthesis of alkenes from aldehydes and ketones

-Ex. slides (16-26)

Step 1: Nucleophilic displacement of iodine by triphenylphosphine

Step 2: Treatment of phosphonium salt w/ very strong base, most commonly BuLi, NaH, or NaNH2

-Exs. slides (16-27)

-Phosphonium ylides react w/ C=O group of aldehydes and ketones to give alkenes

Step 1: Nucleophilic addition of ylide to electrophilic carbonyl C

Step 2: Decomposition of oxaphosphatane

-Exs. slides (16-28, 29)

-Some are Z selective, others E selective

-Wittig reagents w/ anion-stabilizing group (such as carbonyl grp) adjacent to negative charge are generally E selective

-Wittig reagents w/o anion stabilizing group generally Z selective

-Ex. slides (16-30)

-Uses a phosphonoester

*Phosphonoesters prepared by successive SN2 reactions

-Treatment of phosphonoester w/ strong base followed by aldehyde/ketone gives alkene

-Value of using phosphonoester-stabilized anion is that they're almost exclusively E selective

-Exs. slides (16-31, 32, 33)

-Hydration of C=O of aldehyde/ketone gives geminal diol aka gem-diol aka hydrate

-When formaldehyde dissolved in H2O at 20'C, C=O is more than 99% hydrated

-Equilibrium [] of hydrated ketone=much smaller (.1%)

-Exs. slides (16-35)

-Addition of 1 molecule of alcohol to C=O of aldehyde/ketone gives hemiacetal

-Hemiacetals are only minor components of equilibrium mixture, except where a 5 or 6 membered ring can form

*Exs. slides (16-37)

-At equilibrium, Beta anomer of glucose predominates bcuz -OH group on anomeric C is equatorial

*Exs. slides (16-38)

-molecule containing -OH and -OR or -OAr bonded to same C

-Ex. slides (16-36)

-Formation of hemiacetal is base catalyzed

Step 1: Proton transfer from HOR gives an alkoxide

Step 2: Attack of RO- on carbonyl C

Step 3: Proton transfer from alcohol to O- gives hemiacetal and generates new base catalyst

-Exs. slides (16-39)

-Formation of hemiacetal is also acid catalyzed

Step 1: Proton transfer to carbonyl O

Step 2: Attack of ROH on carbonyl C

Step 3: Proton transfer from oxonium ion to A- gives hemiacetal and generates new acid catalyst

Exs. slides (16-40)

-Hemiacetals react w/ alcohols to form acetals

-W/ ethylene glycol and other glycols, product is 5-membered cyclic acetal

Step 1: Proton transfer from HA gives an oxonium ion

Step 2: Loss of H2O gives resonance stabilized cation

Step 3: Rxn of cation (an electrophile) w/ methanol (nucleophile) gives conjugate acid of the acetal

Step 4: Proton transfer to A- gives acetal and generates replacement acid catalyst

-Exs. slides (16-42, 43)

-W/ certain compounds, particular rxns (i.e. Grignard) aren't possible w/o self-destruction

*To prevent this:

1. Protect -CHO group as an acetal

2. Do Grignard rxn

3. Hydrolysis gives target molecule

-Exs. slides (16-46, 47)

-THP protecting group: THP=acetal and stable to neutral and basic solns, and to most oxidizing and reducing agents

*Removed by acid-catalyzed hydrolysis

*Ex. slides (16-48)

-Ammonia, 1' aliphatic amines, and 1' aromatic amines react w/ C=O group of aldehydes/ketones to give imines (Schiff bases)

*Exs. slides (16-49)

-Value of imines is that C=N double bond can be reduced to C-N single bond

*Ex. slides (16-51)

-Rhodopsin is imine formed in eye btwn 11-cis-retinal (vitamin A aldehyde) and the protein opsin

*Ex. slides (16-52)

-Formation of imine occurs in 2 steps:

Step 1: carbonyl addition followed by proton transfer

Step 2: loss of H2O and proton transfer to solvent

-Ex. slides (16-50)

-2' amines react w/ C=O group to form enamines

-Mechanism of enamine formation involves formation of tetrahedral carbonyl addition compound followed by its acid-catalyzed dehydration

-Ex. slides (16-53)

-Carbonyl groups of aldehydes/ketones react w/ hydrazine and its derivatives in manner similar to their rxns w/ 1' amines

*Exs. slides (16-54)

-Hs alpha to carbonyl group are more acidic than Hs of alkanes, alkenes, and alkynes but less acidic than hydroxyl H of alcohols

-This is because the enolate anion is stabilized by:

1. Delocalization of its negative charge

2. Electron w/drawing inductive effect of adjacent electronegative O

-Ex. slides (16-56)

-Protonation of enolate anion on O gives the enol form

-Protonation on C gives the keto form

-Exs. slides (16-57)

-Acid-catalyzed equilibrium of keto and enol tautomers occurs in 2 steps:

Step 1: Proton transfer to carbonyl O

Step 2: Proton transfer to the base A-

-Exs. slides (16-58)

-Keto-enol equilibria for simple aldehydes/ketones lie far toward keto form

*Exs. slides (16-59)

-BUT for certain types of molecules, enol=major form at equilibrium

*Beta-diketones; enol is stabilized by conjugation of pi system of C=C dbl bond and carbonyl grp

*Acyclic Beta-diketones; enol further stabilized by H bonding

*Ex. slides (16-60)

-Oxidized to carboxylic acids by variety of oxidizing agents, including H2CrO4

-Also oxidized by Ag+

*in 1 method, soln of aldehyde in aqueous ethanol or THF is shaken w/ slurry of silver oxide

-Oxidized by O2 in radical chain rxn

*liquid aldehydes so sensitive to air that must be stored under N2

-Exs. slide (16-61, 62)

-Aldehydes can be reduced to 1' alcohols

-Ketones can be reduced to 2' alcohols

-C=O group of aldehyde/ketone can be reduced to -CH2- group

-Ex. slides (16-63)

-Most common lab reagents for reduction of aldehydes/ketones are NaBH4 and LiAlH4

*Both are sources of hydride ion (H:-), a very powerful nucleophile

-Ex. slides (16-64)

-Reductions w/ NaBH4 most commonly carried out in aqueous methanol, pure methanol, or ethanol

-1 mole of NaBH4 reduces 4 moles of aldehyde/ketone

-Key step in metal hydride reduction is transfer of hydride ion to C of C=O group to form tetrahedral carbonyl addition compound

-Ex. slides (16-65, 66)

-Unlike NaBH4, LiAlH4 reacts violently w/ H2O, methanol, and other protic solvents

-Reductions using it carried out in diethyl ether or THF

-Ex. slides (16-67)

-Generally carried out from 25'-100'C and 1-5atm H2

-C=C dbl bond may also be reduced under these conditions

*w/ careful choice of experimental conditions, often possible to selectively reduce C=C dbl bond in presence of aldehyde/ketone

-Exs. slides (16-68, 69)

-Refluxing an aldehyde/ketone w/ amalgamated zinc in concentrated HCl converts carbonyl grp to methylene grp

-Ex. slides (16-70)

-In original procedure, aldehyde/ketone and hydrazine refluxed w/ KOH in high-boiling solvent

-Same rxn can be brought about using hydrazine and potassium tert-butoxide in DMSO

-Ex. slides (16-71)

-aldehydes/ketones w/ at least 1 alpha-H react at an alpha-C w/ Br2 and Cl2

*Rxn catalyzed by both acid and base

-Ex. slides (16-72)

Step 1: Acid-catalyzed enolization

Step 2: Nucleophilic attack of enol on halogen

Step 3: Proton transfer to solvent completes rxn

-Exs. slides (16-73)

Step 1: Formation of enolate anion

Step 2: Nucleophilic attack of enolate anion on halogen

-Exs. slides (16-74)

-Intro of a 2nd halogen is slower than 1st

-Intro of electronegative halogen on alpha-C decreases basicity of carbonyl O toward protonation

-Each successive halogenation is more rapid than previous one

-Intro of electronegative halogen on alpha-C increases the acidity of the remaining alpha-Hs and so each successive alpha-H is removed more rapidly than previous one