Flashcards in Carbonyl Chemistry Deck (32):
What is the carbonyl group?
C = O
Why do compounds containing the carbonyl group have a higher b.p.t than alkanes?
Because molecules of the compound have dipole-dipole interactions, which alkanes do no have.
Why are carbonyl compounds able to form hydrogen bonds with water in spite of the fact no hydrogen is bonded to the oxygen in the carbonyl group?
Because the delta positive hydrogen atoms in the water are attracted to the lone pair on the oxygen.
Why are carbonyl compounds susceptible to nucleophilic attack?
Because the oxygen in the carbonyl group withdraws electron density from the carbon, creating a positive dipole on that carbon. This attracts nucleophiles, which are species which have a lone pair of electrons available for donation to another species.
What are short-chain aldehydes and ketones used for?
Scenting soap and nail varnish remover.
Why are hydroxynitriles not made in the lab using hydrogen cyanide?
Because hydrogen cyanide is toxic.
How can a hydroxynitrile be formed?
By reacting a ketone or aldehyde with acidified potassium cyanide.
What is the mechanism for the formation of a hydroxynitrile?
Addition - the C=O bond is broken.
Describe a test for asserting the presence of an aldehyde in solution.
Fehling's test: Contains Cu²⁺ ions, an alkali and a completing agent.
If an aldehyde is present when the solution is warmed with Fehling's a brick-red p.p.t will form (Cu₂O).
Describe a test for asserting the presence of a ketone in a solution.
Tollens' reagent: formed by reacting ammonia with silver nitrate.
NH₃ +AgNO₃ ---> [Ag(NH₃)₂]⁺
Reduction by an aldehyde:
Forms Ag and 2NH₃
The silver colors the solution.
How is it possible to form a primary alcohol from a carbonyl-containing compound?
By reducing an aldehyde with sodium tetrahydridoborate (NaBH₄) in solution.
RCHO + 2[H] ---> RCH₂OH
Why are esters more volatile than carboxylic acids?
Because esters do not form hydrogen bonds - carboxylic acids do. Weaker IMFs between ester molecules mean that less energy is required to initiate the state change.
What is a fat/oil?
A long-chain ester formed from glycerol.
What are the steps in the hydrolysis of methyl ethanoate with a sodium hydroxide catalyst?
H₂O + CH₃COOCH₃ ---> CH₃COOH + CH₃OH
CH₃COOH + NaHCO₃ ---> CH₃COO⁻Na⁺ + H₂O + CO₂
What is the IUPAC name for glycerol?
Propane - 1,2,3 - triol.
What is a sodium salt of a fat?
A sodium carboxylate. (I.e. An ester with a sodium group rather than an alkyl group)
What is a use of sodium carboxylates formed by boiling sodium hydroxide with fats?
What are some uses of glycerol?
Plasticizer - allows polymers to slip over one another.
Solvent - toothpaste and food coloring.
Hydrating agent - used in pharmaceuticals.
How, in words, can biodiesel be formed?
By reacting long-chain triglycerides and methanol in the presence of a potassium hydroxide catalyst.
How can an ester be converted to its parent acid and alcohol?
By refluxing the ester with a dilute acid - acid hyrolysis.
By refluxing the ester with dilute alkali - this forms the salt of the acid and the reaction can go to completion.
Why are fats solid, but oils not?
Fats are saturated hydrocarbons - they tessellate and have strong Van der Waals between molecules.
Oils are unsatuated hydrocarbons, meaning that they do not tessellate and have weak Van der Waals.
How is it possible to form glycerol and a sodium carboxylate from a fat?
By boiling the fat with sodium hydroxide.
How can a sodium carboxylate be converted to an acid?
By reacting the sodium salt with an acid.
Why is biodiesel not carbon neutral?
Fossil fuels are sometimes burned when making fertilizer and planting, harvesting and converting the oil.
What is the suffix for the acyl chloride functional group?
What is formed in the reaction between water and an acyl chloride?
A carboxylic acid and HCl gas.
How is it possible to determine that a reaction is between ammonia/water/an alcohol and an acyl chloride?
By observing whether the reaction gives off fumes - HCl gas.
What temperature is the reaction between an acyl chloride and alcohol conducted at?
Room temperature, same as with all acyl chloride + nucleophile reactions.
Why is it preferable to use an acid anhydride over an acyl chloride in industry?
Acid anhydrides are cheaper, less corrosive, react less violently and do not produce toxic HCl gas.
What mechanism are the reactions between acyl chlorides and a nucleophile?
Nucleophilic addition-elimination reactions.
What is aspirin? How is it produced?
An ester. It is produced by reacting salicyclic acid with ethanoic anhydride.