Carbonyls & Carboxylic Acids
No description yet. This curated deck is ready for daily study.
Card preview (24)
What type of reaction converts an aldehyde/ketone back to an alcohol?
Reduction
What nucleophile does NaBH₄ supply in the mechanism of ketone/aldehyde reductions?
H- ions
What reagent is needed to reduce aldehydes and ketones to alcohols?
NaBH₄
When writing an equation for a ketone or aldehyde reduction, how should the reducing agent be represented?
[H]
During a ketone/aldehyde reduction, what 2 reagents act as acceptable solvents?
Water or ethanol. 99% of the time, water is used in exam questions.
What are the steps to draw a complete mechanism for the reduction of an aldehyde or ketone?
• Add the neucleophile, H-. The ion must have a lone pair. • Draw a curly arrow from the lone pair to the carbon atom in the C=O bond. • Add a positive dipole onto the C and a negative dipole onto the O. Draw a curly arrow from the double bond to the oxygen. • Form the unstable intermediate by breaking the double bond. Add the hydrogen(s) that have now bonded. Make sure the oxygen on the organic intermediate has a lone pair and a full negative charge. • Draw a displayed water molecule. Add a + dipole onto the H and a - dipole onto the O. Draw one curly arrow from the lone pair on the organic intermediate oxygen to the hydrogen on water and one from the O-H bond to thr oxygen in the water molecule. • Form the alchohol and add + OH- on the end
What are the reagents needed to add cyanide to a carbonyl compound by reduction?
• Sodium cyanide (NaCN) • Concentrated sulphuric acid
What is the steps to draw a complete mechinism for the addition of cyanide to a carbonyl compound?
• Draw the CN- neucleophile. A lone pair should be present on the carbon, a triple bond between the carbon and nitrogen and a full negative charge on the nitrogen. • Draw a curly arrow from the lone pair on the CN- carbon to the carbon on the C=O. Draw a second curly arrow from the double bond to the oxygen. Add relevant dipoles to the C=O. • Form the unstable intermediate. The CN should be bonded onto C1 with an oxygen adjacent to it. Add a lone pair and a full negative charge to this oxygen. • Add a H+ ion above the oxygen and draw a curly arrow from the lone pair on the oxygen to the hydrogen. • Form the final product with the OH group on it.
What is the name of the group of compounds formed when HCN reacts with a carbonyl compound?
Hydroxy nitriles
How are hydroxynitriles named?
• Always include the carbon on the CN as part of the chain • CN will always be Carbon 1 • 2-hydroxy butane nitrile
What 2 compounds must 2-4 DNP be dissolved into for a result to occur?
Methanol and sulphuric acid
What is the positive result during a 2-4 DNP test?
A bright orange ppt will be formed
What compounds does 2-4 DNP not detect?
• Esters and carboxylic acids • Only aldehydes and ketones will produce a positive result with 2-4 DNP
What is the method to identify an organic unknown compound usinng 2-4 DNP?
• Take a sample of the compound and add 2-4 DNP, see if an orange ppt is formed. • Filter off the crystals using a buchner funnel and water pump to aquire an impure solid. • Dissolve the crystals in the minumum amount of a hot ethanol solvent • Add the test tube to ice cold water to allow the pure solid to recrystalise • Filter the crystals off using the buchner funnel • Find the melting point and compare to a known chemical data base to find the compound
What is the carboxylate ion?
COO-
What reaction occurs when a carboxylic acid reacts with a metal?
• A carboxylate salt (e.g. Sodium ethanoate) is formed • Hydrogen gas is also made as a byproduct • The H in the O-H is replacted by the metal ion. Both the O and the metal have fulll charges.
What changes when a carboxylic acid reacts with a group 2 metal, compared to a group 1 metal?
• To cancel the 2+ charge on the metal, 2 COO- ions are needed • As such, place brackets and a subscript 2 around the COO- and put the 2+ ions on the outside of that bracket
What is the definition of a carboxylic acid derivative?
A compound that can be hydrolysed to form the parent carboxylic acid that it came from
How is an ester appropriately named?
• Name the alcohol part first and add yl on the end • Name the acid part next. Add ate onto the end (e.g. ethanoate) • Add on any groups
What is the definition of esterification?
Where an alcohol and a carboxylic acid react together to form an ester and water.
What type of reaction is esterification?
A condensation reaction
What are the reagents and conditions required for esterification?
Sulphuric acid catalyst and heat
How is an acid anhydride formed?
Water is removed from 2 molecules of a carboxylic acid
What does the top part of an acid anhydride react with during esterification?
Reacts with the alkyl group of the alcohol to form the ester