Aldehydes and Ketones Flashcards
Put the following in order of decreasing boiling point: Butanol Propane Propanol Propanal
Butanol Propanol Propanal Propane
If this molecule were reacted with a strong base, which atom would be deprotonated?
The hydrogens on an alpha carbon, which are known as alpha-hydrogens, are weakly acidic and can be removed by a strong base. Thus, when combined with a strong base, the alpha-carbon of the ketone in question will be deprotonated. Only the alpha carbon to the right of the carbonyl has hydrogens and is therefore the only candidate for deprotonation.
Place the following on order of decreasing acidity:
Propanal
Propanoic acid
Propanedial
Propanone
Propanoic acid
Propanedial
Propanal
Propanone
True or False: Aldehydes are more acidic than ketones
True:
In general, ketones are less acidic than aldehydes, since the other flanking alkyl group is slightly electron-donating, destabilizing the negative charge of the enolate conjugate base.
NaH
Strong BASE
True or False: the alpha hydrogens of the betadicarbonyls are more acidic than normal cabonyls
true because you got double the trouble
What are the three major characterstics that both aldehydes and ketones share?
Polar, aprotic, H-Bond acceptors
Rank the following in terms of decreasing boiling point:
Pentanoic acid
Pentanal
Pentane
Pentanol
Pentanal
Pentanoic acid
Pentanol
Pentanal
Pentane
How would you oxidize an aldehyde to a carboxylic acid?
Jones reagent, CrO3, NacCr2O4, K2Cr2O7,KmnO4
True or False: You can oxidize an aldehyde to a carboxylic acid using PCC
No, it is a weak oxidizing agent
How can you make an alcohol from aldehydes or ketones?
NaBH4 or LAH
Reducing agent
True or False: The carconyl carbon of a ketone is more positively chares than that of an aldehyde
False: In a ketone, each carbon atom bonded to the carbonyl donates a small amount of electron density, and thus negative charge, to the carbonyl carbon. This reduces, not increases, the net positive charge on the carbonyl carbon of ketones relative to aldehydes, and is another reason that ketones are less electrophilic than aldehydes.
The first step of this reaction can best be described as:
NUCELOPHILLIC ADDITION. The figure depicts a Grignard reaction, a highly useful organometallic reaction used to form carbon-carbon bonds. The carbon-magnesium bond is polarized, giving the carbon a partially negative charge. As such, this carbon atom can act as a nucleophile and attack the partially positive carbonyl carbon on acetone to form an alcohol.
How would you make an imine from a carbony?
In this reaction, the nitrogen from the amine essentially replaces the carbonyl oxygen, forming a carbon-nitrogen double bond, as shown below.
The reaction below involves a symmetric ketone with a primary amine. What is the final product of this reaction?
What does a hemiacetal vs a hemiketal look like?
How would the pka of the hydrogens on the alpha carbon in the picture compare to the pka of those found in something like 2-butanone?
The pKa would be lower for the ones in acetylacetone (~9) compared to those found in 2-butanone (~14.7). They are more acidic becuase of the electron drawing groups on either side of them.
What would happen if I treated the following with Na2Cr2O7?
Nothing would happen because it cannot be oxidized further. If it were a terminal carbonyl like an aldehyde it could be oxidized further but its not.
What would happen if I treated the following with a strong oxidizing agent?
It would oxidize to a carboxylic acid
What would happen if I treated the following with NaBH4 or LiAlH4?
It would be reduced to a secondary alcohol
