Carbonyls Flashcards
What is a carboxylic Acids Functional Group
-COOH
C=O and C-OH
Explain a Carboxylic Acids Solubility
C=O, C-O and O-h are all polar bonds and therefore are attracted to the polar elements within water molecules
Acid Groups can form hydrogen bonds with water molecules. due sufficient polarization of the O-H bond, Delta positve Hydrogen forms a weak bond with lone pair on a waters oxygen.
What are the intermolecular forces in Carboxylic acids
Hydrogen Bonds in the solid State
Very Strong
Permanent Dipole Dipole due to large electronegative differences
VDW
What are Esters?
How are they Formed ?
Functional Group?
General Formula?
Formed from carboxylic acids and alcohols
RCOOR’ C=O C-O-C
1
propyl ethanoate
How do you name esters
Starts with the group that has replaced the hydrogen on the carboxylic acid.
Then alcohol part eg. Propyl for Propanol
Then Eg. Ethanoate (from carboxylic acid)
eg. Butyl Propanoate
Name the Physical properties of esters (2)
Sweet Smelling (usually similar to fruits)
Volatile liquids
What are some of the uses of an ester
Flavourings, perfumes solvents and plasticiser
What are some common natural esters
Fats and oils
Draw the Polarisation of a carboxylic acid
1
Write an Equation for the Equilibrium formed by ethanoic acid in Solution
What happens to the negative charge on the ethanoate ion in terms of electrons
Electrons delocalise so the negative charge is shared across the whole carboxylate group
How do you distinguish Carboxylic acids from other -OH containing Compounds?
Write Equation
1) Add NaHCO3 (sodium hydrogen carbonate) or Na2CO3 Sodium Carbonate
Acids will produce Sodium salt, water and carbon dioxide
Can recognise carbon dioxide emissions from effervescence
Write and equation for the reaction of ethanoic acid with NaOH
1
What Catalysts are needed for the formation of esters from alcohols and carboxylic acids
Strong Acid
Which alcohol forms the esters that make up animal and vegetable oils
Glycerol/ propane-1,2,3-tirol
What is the difference between an oil and a fat
Oils are liquid esters at room temperature
fats are solids esters
Fats are usally saturated
oils are usually not
What are the Products of hydrolysing fats and oils? (NaOH)
Propane-1,2,3 tirol and sodium salts of the acids that make the ester (hydrolysed NaOH)
What is the use of the sodium salt of an ester
How does the product do this?
Soaps (carboxylate ion)
Long hydrocarbon non polar chain attaches to dirt
The polar COO- end is polar and is soluble in water
This allows dirt to be removed more effectively then water alone
What are the common uses of glycerol
Prevents the drying out of creams
Solvents in Medicine and food items such as food colouring
Plasticising materials
How do you make Biodiesel
General Equation and Conditions
What is Biodiesels functional group
NaOH Catalyst
60 Degrees
Lipids (fats/oils -esters) + 3 CH3OH —> 3 Methyl esters + Glyserol
Biodiesel - R-CO2CH3 R is a fatty acid
What is transesterfication
Conversation of 1 ester to another
What Crops are used to make BioDiesel
Rapeseed or soybean oil
How is the reaction mixture of Biodiesel Purified and separated
How is Biodiesel production a problem
Centrifuge then Add acid to neutralise excess alkali catalyst. Solid Salt/Soap forms which is removed by filtering.
Crops used to create food are being used to create fuel
What are carboxylic acid Derivatives
Molecules that have the acyl group as a part of their structure, formed from carboxylic acids
Name two carboxylic acid derivatives and their Functional Group formulas
Acyl Chloride : RCOCl C=O and C-Cl
Acid Anhydrides: RCOOOCR
Draw the Mechanism for the acylation of a nucleophile (Add-Elim)
1
What factors Determine how readily the acylation of a nucleophile by an acid derivative occurs (3)
Magnitude of the Delta positive charge on the carbon from the per ant dipole caused by the Delta Negative atoms
How easily does the leaving party leave the molecule
How Readily does the nucleophile donate electrons
What effect do the Cl and O atoms in the Acyl Chrloride and Acid anhydrides have on the partial charge of the carbonyl carbon
Increase the Delta Positive charge on the carbon by attracting electrons (negative inductive effect) this means the carbon redacts more readily with nucleophiles
Are Acyl Chlroides or Acid Anhydrides more reactive
Acyl Chlorides
How do you produce an amide form an acid anhydride/ Acyl chloride
Show Mechanism (use Ethanoyl Anhydride)
1) React with NH3
(reform the double bond on other molecule)
What is the Equation and Mechanism for the reaction between ethanoyl chloride and ammonia
CH3COCl + 2NH3 —> CH3CONH2 + NH4Cl
If a nucleophile is a primary amine what are the products of the acylation of acyl chlorides or acid anhydrides
N-Substituted Amides
What are the products to the acylation of a Acid Derivate and an Alcohol?
Draw the mechanism of Ethanyl chloride and ethanol
and the general equation
An Ester
If the Nucleophile is water what are the products of the acylation of acyl chlorides /acid anhydrides with water?
Draw the mechanism and a general Equation
Carboxylic acid (Hydrolysis)
The product of the Hyrdolysis of acid derivatives are primarily used for which purpose?
Manufacture of Aspirin
What are the advantages to using acid anhydrides to acyl chlorides (3)
Cheaper.
Less corrosive and does not react readily water
Safer as ethanoic acid is produced rather then HCl (corrosiveP
What would you observe n a melting point determination if the sample wasn’t pure?
Sample would melt over a large range of temperatures
Sample melting point is below accepted value due to impurities disrupting the structure.
What conditions are needed for the formation of methyl esters from acid anhydrides or acyl chlorides
Alcohol reactant such as methanol
And heat gently under reflux
Hydrolysis - Alkali catalyst
When undergoing recrystallisation why is there a minimum volume of solvent
So a saturated solution is formed
So that as many crystals as possible form when cooled
Why is the solution filtered hot when purifying by recrystallisation
why is the solution cooled in an ice bath?
To remove insoluble impurities and ensure that the crystals do not form in the filter paper.
To increase the yield of crystals so more are formed
Why are crystals washed with cold water when repurifying by recrystallisation
To remove soluble impurities
At what times do you use a büchner funnel in the preparation, recrystallisation and purifying of an organic solid.
1) Filter under reduced pressure - separate the solid from the crude ,after the reaction to form the solid
2) Filter under reduced pressure - after the recrystallisation of the crystals to filter them off.
3) Drying of product - Sucking air over the solid then placing in a low temperature oven
Prepping of an organic solid
1
What is the Carbonyl Group
C=O
What is the Functional Group and general Formula for a aldehyde
RCHO C=O and C-R,C-H
HO not OH
What is the Functional Group of a ketone?
RCOR’
C=O and ,C-R C-R’
How do you name aldehydes
-al suffix
How do you name ketones
-n-one suffix
where n is the carbon which the C=O is on
What kind of intermolecular forces do the carbonyl group have?
Permanent Dipole Dipole due to large electronegative difference between C and O in the polar C=O bond
How Soluble are carbonyls in water?
What is the trend?
Yes- dipole dipole intermolecular forces between molecules between water molecules and oxygen in the C=O bond
As Chain length increases solubility decreases
Which part of a carbonyl group is reactive and why?
C=O, due to the polarity of the bond (large differences in electronegativity) and high electron density
Draw the Mechanism of a aldehyde with the addition of a nucleophile
Nucleophilic addition (not elimination)
Produces a Hydroxy________
Usually CN: is used that would be Hydroxy-Nitrile
Nucleophilic addition of HCN and a carbonyl produces (2)?
A HydroxyNitrile
:CN can attack above or below the planar C=O group with equal likelihood, producing a pair of enantiomers each with a chiral carbon if an unsymmetrical ketone or aldehyde is reacted
Electrophilic Addition
What is Fehlings? How does it React
gentle oxidising agent
Heat Blue copper (II) complex ions is reduced to Cu+ ions which is the colour of brick red if there is an alcohol or aldehyde present
What is Tollens Reagent? How does it React?
Silver nitrate with 1 drop of sodium hydroxide in excess NH3(aq)
Oxidises aldehydes and alcohols ( not ketones)
Complex silver (I) ions are reduced to a silver precipitate which forms a silver mirror within the test tube.
Ag+ +e- ———> Ag(s)
What is the potassium dichromate colour change when reduced?
H2SO4 with K2Cr2O7
Goes from Orange —> Green (something has been oxidised)
Dichromate(IV) ions = Orange
Chromium(Cr3+) Ions = green
What is a reducing agent commonly used for for ketones aldehydes and alcohols
LiAlH4 (Lithium aluminium hydride)
NaBH4 (Sodium tetrahydridoborate)
Both Release a hydride ion
Draw the mechanism for the reduction of an aldehyde
Nucleophilic addition.
Draw the Mechanism for the electrophilic addition of sulphuric acid to ethene
Ethyl Hydrogen Sulphate
In a reaction to from Biodiesel
1 Mol of vegetable oil reacts with excess methanol to form 2 mol of an ester C19H34O2 and 1 mol of an ester C19H36O2
Draw the structure of the vegetable oil.
You may Abbreviate the hydrocarbon Chain.
