C26 Carbonyls And Carboxylic Acids Flashcards
What’s the carbonyl group
C=O
What’s the functional group and general formula for an aldehyde
RCHO (C double bonded to O, single bond to H and R)
What’s the functional group for a ketone
RCOR’ (C double bonded to O)
How do you name aldehydes
-al suffix (C=O is on the end of a chain)
How do you name ketones
-one stuffix (designate number for which carbon C=O is on)
What kind of intermolecular forces do molecules with the carbonyl group have? Why?
Permanent dipole-dipole due to the polar C=O bond
How soluble are they in water? What influences solubility?
Form hydrogen bonds between water molecules and oxygen of C=O. As C chain length increases, solubility decreases
Which bond in carbonyl compounds is usually involved in reactions? Why?
C=O, due to the polarity of the bond (large difference in electronegativity between C and O)
What’s the strongest bond in carbonyl compounds
C=O
Why’s the addition of HCN important
Increases the length of the carbon chain by one carbon atom allowing more useful molecules to be made
Will the product of HCN added to a carbonyl compound have optical isomers? Why?
Yes they will. In the aldehyde/ketone, the carbonyl carbon is planar, so the :CN^- can attack from either above or below, forming 2 enantiomers
What’s the name of the product when HCN is added to a carbonyl compound
Hydroxynitrile (have OH and CN groups)
What’s Fehling’s solution? What’s Colour is it?
Copper complex ions, blue
What happens when an aldehyde is added to Fehling’s solution
Reduced to Cu^+ ions —> colour change to brick red ppt
What happens when a ketone is added to Fehling’s solution
No visible change —> stays blue
How do you test for a carbonyl compound
Use Brady’s reagent - 2,4-DNP
If a carbonyl compound is present an orange precipitate is formed
What’s is in tollens’ reagent
Silver complex ions in colourless solution
What happens when an aldehyde is added to Tollen’s reagent
Silver mirror forms as Ag+ reduced to Ag(s)
What happens when a ketone is added to tollen’s reagent
No visible change
What’s another oxidising agent for alcohols and aldehydes? What change in colour does this undergo?
Acidified potassium dichromate (VI) - H2SO4 and K2Cr2O7
Colour change from orange to green
What’s a reducing agent for aldehydes and ketones? What ions does this release in solution?
NaBH4 [sodium tetrahydridoborate (III)] releases an H- ion
How do you convert an aldehyde to form a carboxylic acid
Oxidation of aldehydes using Cr2O7^2-/H+ (i.e. K2Cr2O7/H2SO4)
What’s the functional group of a carboxylic acid
-COOH (C=O and C-OH)
How do you name carboxylic acids?
-oic acid
Are carboxylic acids soluble in water? Why? What influences their solubility?
Yes
Acid group can form hydrogen bonds with water molecules
What are the IMF’s in carboxylic acids
Hydrogen bonds in solid state - very strong
What are esters (what are they formed from)? Functional group, general formula?
Formed from carboxylic acids and alcohols.
RCOOR’ (C=O, C-O-C)
How do you name esters?
Start with the alcohol group that has replaces the hydrogen, the acid part e.g. propyl (from alcohol) ethanoate (from carboxylic acid)
What characteristic physical properties do esters have
Volatile, pleasant fruity smells e.g. apple, pear drops
What are some uses of esters
Flavourings, perfumes (both for longer chains), solvents (short chains), plasticisers.
How could you distinguish carboxylic acids from other -OH containing compounds?
Add NaHCO3, acids will produce sodium salt, water and carbon dioxide
What catalyst is needed for the formation of esters from alcohols and carboxylic acids
Concentrated strong acid e.g. H2SO4
What catalyst is needed for the hydrolysis of esters
Dilute strong acid e.g. H2SO4
What’s an alternative method of hydrolysis
Base hydrolysis
What are the advantages of base hydrolysis
Reaction goes to completion due to neutralisation by base - more product in the mixture than acid catalysed hydrolysis
What are carboxylic acid derivatives
Molecules that have the acyl group as part of their structure, formed from carboxylic acids
Name 2 acid derivatives and give their functional groups
Acyl chlorides: RCOCl
Acid anhydrides: RCOOCR/(RCO)2O
How do you form an acyl chloride
React a carboxylic acids with SOCl2
If the nucleophile is ammonia for the acylation of acyl chlorides or acid anhydrides, what are the products of the reaction
An amide
If the nucleophile is a primary amine, what are the products of the acylation of acyl chlorides or acid anhydrides
N-substituted amide
If the nucleophile is an alcohol, what are the products of the acylation of acyl chlorides or acid anhydrides
An ester
If the nucleophile is water, what are the products of the acylation of acyl chlorides or acid anhydrides
Carboxylic acid (hydrolysis produces an ester linkage)
What’s the name of the acylation of acyl chlorides/acid anhydrides with water as a nucleophile?
Hydrolysis
Hydrolysis
