Organic chem - 4 Flashcards
What does planar carbon refer to?
A carbon that does not have four single bonds./ Any carbon that is not tetrahedral.
Aldehydes are a ………… series, containing the - CHO functional group
- Homologous
- CHO
What is aldehydes general formula?
RCHO
What is ‘R’ in RCHO?
Either a hydrogen atom or an alkali group.
What group do aldehydes contain in their structure?
A carbonyl group.
What is a carbonyl group?
C = O
Is the carbonyl group in aldehydes polar or non-polar?
Polar
Why is the carbonyl group in aldehydes polar?
Due to the difference in electronegativity value of the carbon and oxygen atoms.
Is the oxygen delta + or delta - ? (In general formula)
Delta -
Is the carbon delta + or delta - ? (In general formula)
Delta +
Why is the oxygen delta - ? (In general formula)
Because it is more electronegative.
Why is the carbon delta + ? (In general formula)
As it is less electronegative.
What forces of attractions are between the aldehyde molecules?
Dipole-dipole attractions.
Why is there dipole-dipole attractions between aldehydes?
Due to the carbonyl group.
What has higher boiling points, alkanes or aldehydes?
Aldehydes
What has higher boiling points, alcohols or aldehydes?
Alcohols
Are the lower aldehydes soluble or insoluble in water?
Soluble
Are the lower aldehydes soluble or insoluble in non-polar solvents such as cyclohexane?
Soluble
Name a non-polar solvent that the lower aldehydes are soluble in.
Cyclohexane
Why are the lower aldehydes soluble in water, a polar solvent?
Due to the hydrogen bonding that occurs between the oxygen of the carbonyl group of the aldehyde and the hydrogen of water.
Are the higher aldehydes soluble or insoluble in water?
Insoluble
Why are the higher aldehydes insoluble in water?
As the non-polar chain of the aldehyde molecule has greater influence.
What will aldehydes end in when naming?
- anal
Name 3 examples of aldehydes and draw them.
- Methanal
- Ehanal
- Propanal
Methanol at r.t
- Gas
Ethanal at r.t
- Volatile gas
Where is the functional group always written?
To the right of the molecule
What is the carbon of the functional group always when naming?
C1
What does solubility depend on?
The length of the carbon chain.
What is another name for methanal?
Formaldehyde
Draw methanal and give its molecular formula.
- HCHO
Draw ethanal and give it’s molecular formula.
- CH₃CHO
Draw propanal and give it’s molecular formula.
- C2H5CHO
Draw butanal and give it’s molecular formula.
- C₃H7CHO
How many structural isomers does C4H8O have?
3
Name the three isomers of C4H8O
- Butanal
- 2 methylpropanal
- Butanone
What are aldehydes isomers of?
Ketones
What are aldehydes and ketones?
Aldehydes of each other
What is benzaldehyde?
An aromatic aldehyde.
What is another name for benzaldehyde?
Phenylmethanal
Where is phenylmethanal (benzaldehyde) found?
In almond oil of almond kernels found.
What is ketones general formula?
R1COR2
What is R1 and R2 in R1COR2?
Alkali groups which may be the same or different.
What can’t R1 and R2 be?
Hydrogen
What do ketones contain in their functional group other than alkali groups?
A carbonyl group
What is the carbonyl group in ketones?
- C = O
What do the physical properties of ketones show a lot of similarities to?
Aldehydes.
What has a higher boiling point aldehydes or ketones?
Ketones
Why do ketones have higher boiling points than aldehydes?
Due to the dipole-dipole attractions between the polar carbonyl groups.
What has higher boiling points, ketones or alcohols?
Alcohols.
Are the lower ketones soluble or insoluble in polar water?
Soluble
Why are the lower ketones soluble in water?
Due to the hydrogen bonding between the oxygen of the carbonyl group of the ketone and the hydrogen in water.
When does the solubility in water decrease?
As the length of the non-polar carbon chain increases.
Are ketones soluble or insoluble in non-polar solvents such as cyclohexane?
Soluble
Name a non-polar solvent that ketones are soluble in.
Cyclohexane
Is propanone a polar or non-polar solvent?
Polar
Where is propanone found?
In nail varnish remover
What is another name for acetone?
Propanone
What does naming ketones end in?
- Anone
Name two examples of ketones.
- Propanone
- Butanone
What is the carbon of the functional group never? (ketones)
The first or last carbon of the molecule.
What is the position of the carbon of the functional group of ketones indicated by?
By the smallest possible number.
What is the first member of the homologous series? (ketones)
Propanone.
Why is propanone the first member of the homologous series (ketones) ?
As ketones can only have a minimum of 3 carbons in the chain.
What is propanone?
A solvent in nail polish remover.
Draw the structure formula of propanone and give it’s molecular formula.
- CH3COCH3
Draw the structure formula of butanone and give it’s molecular formula.
- CH₃COC₂H5
What is the carboxylic acid’s general formula?
RCOOH
What is R in the carboxylic acid’s general formula?
Either hydrogen or an alkali group.
What is the functional group of carboxylic acid?
- COOH
What has higher boiling points, carboxylic acids or the corresponding alcohols?
Carboxylic acids
Why do carboxylic acids have higher boiling points than the corresponding alcohols?
Due to the hydrogen bonding present between molecules caused by the polar -OH group present in the functional group.
What is the hydrogen bonding between molecules in carboxylic acids caused by?
The polar -OH group present in the functional group.
What do the molecules of carboxylic acids group together in?
Twos
What are the twos that carboxylic acids group together in called?
Dimers
What are the dimers held together by?
Hydrogen bonds.
What has the highest boiling points of all the homologous series?
Carboxylic acids
What do the dimers that are held together by carboxylic acids cause?
More energy is need to break them down.
What are carboxylic acids at r.t?
Liquids
Why are carboxylic acids liquids at r.t?
Due to the hydrogen bonds holding the molecules together.
Are the lower carboxylic acids soluble or insoluble in water?
Soluble
Why are the lower carboxylic acids soluble in water?
Due to the formation of hydrogen bonds with water
What does the oxygen of the carbonyl group in carboxylic acids form with in water?
The oxygen of the carbonyl group of the acid forms a hydrogen bond with the hydrogen in water.
What does the hydrogen of the -OH group of the acid form?
Forms another hydrogen bond with the oxygen of water.
What happens as the length of the carbon chain increases?
Solubility decreases
Are the higher members of carboxylic acids soluble or insoluble in non-polar solvents?
Soluble
Name a non-polar solvent that the higher members of carboxylic acids are soluble in.
Cyclohexane
When naming the carboxylic acids. where is the functional group?
Always on the right hand side of the molecule
The right hand side of a carboxylic acids molecule is always….
C1
What are the endings of carboxylic acids?
- anoic acid
Name 3 examples of carboxylic acids.
- Methanoic acid
- Ethanoic acid
- Propanoic acid
Give another name for methanoic acid
Formic acid
Where is methanoic acid found?
In nettle and stinging ants
What manufacturing is ethanoic acid involved in?
- Manufacture of cellulose acetate, which is used in varnishes
Where is ethanoic acid found?
In vinegar
Name an aromatic carboxylic acid.
Benzoic acid
What is propanoic acid and benzoic acid used as?
Food preservatives
Name an unusual carboxylic acid and why it’s unusual.
- Methanoic acid
- As it can act like an aldehyde
Why can methanoic acid act like an aldehyde?
As its structure contains the aldehyde functional group.
Give the molecular formula and draw methanoic acid/formic acid.
HCOOH
Give the molecular formula and draw ethanoic acid / acetic acid.
CH₃COOH
Give the molecular formula and draw propanoic acid.
C₂H5COOH
Give the molecular formula and draw butanoic acid.
C₃H7COOH
Name 2 carboxylic acid that are used as food preservatives.
- Benzoic acid
- Propanoic acid
What is the general formula of esters?
R1COOR2
What is R1 in the general formula of esters?
Either a hydrogen or and alkyl group.
What is R2 in the general formula of esters?
An alkyl group
How are esters formed?
Formed by the reverse reaction between a carboxylic acid and an alcohol.
What is the formation of esters caused by the reverse reaction between a carboxylic acid and an alcohol called?
A condensation reaction
When does a condensation reaction occur?
When two different molecules combine to form a more complex molecule with the production of a smaller molecule such as H2O.
Do esters have relatively high or low boiling points?
Relatively low boiling points
What forces of attraction is present between ester molecules?
Dipole-dipole
Why do esters have relatively low boiling points?
Due to the dipole-dipole attractions between molecules.
Are the lower esters soluble or insoluble in polar water?
Soluble
Why are the lower esters soluble in polar water?
As the oxygen of the carbonyl group forms hydrogen bonds with the hydrogen of water.
What happens to the solubility of esters as the carbon chain length increases?
It decreases
Are the higher esters soluble or insoluble in non-polar solvents?
Soluble
Name a non-polar solvent that the higher esters are soluble in.
Cyclohexane
Name two homologous series that are isomers of each other.
Carboxylic acid and esters
What are the names of the 2 isomers of C3H6O2
Propanoic acid and methylethanoid
What can’t be forgotten when writing out a condensation reaction equation?
Don’t forget the H2O
What is the first step in condensation reactions?
Take the H out of the functional group
Where does R1 of the ester of the carbon of the functional group come from?
The carboxylic acid
Where does the R2 of the ester come from?
The alcohol
How are esters named?
‘Backwards@
What end comes first when naming esters?
The alkyl group of the end of the molecule
What ending is given to the alkyl group of the end of the molecule in esters?
-yl
What ending is given to the front part of the molecules in esters?
-anoate
Which parts of ethyl butanoate were originally homologous series?
ethyl - alcoholl
butanoate - carboxylic acid
Name the molecule CH3COOC2H5
- End is ethyl
- Front is ethanoate
= Ethyl ethanoate
Name the molecule HCOOC3H7
- End is propyl
- Front is methanoate = propyl methanoate
Name the molecule HCOOCH3
Methyl formate
Name the molecule C2H5COOC2H5
Ethyl acetate
Write the formula for butyl ethanoate
C₆H12O₂
Write the formula for propyl methanoate
C₄H₈O₂
Write the formula for ethyl propanoate
C5H10O₂
Write the formula for ethyl ethanoate
C₄H₈O₂
What does ‘poly’esters mean?
Many
What name is given to synthetic fabrics such as ‘terylene’?
Polyesters
What are polyesters used for?
Used in the clothing industry and other fabric industries i.e carpet, sails etc.
What are polyesters?
Polymers what consist of hundreds of thousands of ester molecules liked together under certain conditions of temperature and pressure.
Are polyesters found naturally or artificial?
Artificial
Name 2 esters that occur naturally
Fats and oils
Give an example of an ester that occurs naturally which is used to make soap.
Glyceryl tristearate
What role is glyceryl tristearate in the preparation of soap?
The limiting reactant
Basic meaning of limiting reactant
The one that runs out first
Find the molecular mass of glyceryl tristearate
890
Learn the structure of glyceryl tristearate!!
DONE
What is noticable upon dealing with esters?
They have distinct aromas (smells)
Name 2 smells that esters are responsible for?
- petals of flowers
- fruits
4 examples of the use of synthetic esters
- perfumes
- soaps
- bath salts
- deodorants
Why are synthetic esters manufactoured?
To imitate smells for use in perfumes etc.
What is ethyl ethanoate used as?
A non-polar solvent
Why are the preparation of aldehydes, ketones and a carboxylic acids, redox reactions?
As the alcohol is oxidised and the oxiding agent(sodium dichromate) is reduced during the preparation..
What is the oxidising agent in the preparation of aldehydes, ketones and carboxylics acids?
Sodium dichromate
What does the reduction of the dichromate ion during redox reactions lead to?
A colour change of orange to green as Cr(+6) is reduced to Cr(+₃)
What is reduced during redox reactions?
Dichromate ion
Name all 3 reactions of ethanal
- With acidified potassium permanganate
- With Fehling’s solution
- With Tollen’s Reagent
What are the steps in the reaction of ethanal with acidified potassium permanganate?
- Place a few cm3 of ethanal into a test tube with some acidified permanganate (VII)
- Heat gently in a water bath for a few minutes
What colour is Fehling’s solution?
Blue
What colour is potassium manganate (VII)?
Purple
What is the result of the reaction of ethanal with acidified potassium permanganate?
Manganate (VII) purple → colourless
What does the manganate (VII) go from purple to colourless in the reaction of ethanal with acidified potassium permanganate?
As the ethanal is a reducing agent and reduces Mn(+7) to Mn(+₂).
What is the equation for the reaction of ethanal with acidified potassium permanganate?
CH3CHO+Mn(+7) → CH3COOH +Mn(+₂)
What are the steps in the reaction of ethanal with Fehling’s solution
- Place a few cm3 of ethanal into a test tube.
- Add equal volumes of Fehlings solution A+B
- Heat gently and shake to mix
What colour occurs when equal volumes of Fehlings solution are added in the reaction of ethanal with Fehling’s solution and why?
Blue due to the presence of Cu(II).
What is the result in the reaction of ethanal with Fehling’s solution?
Fehlings solution blue → red precipitate
Why does the colour change to red in the reaction of ethanal with Fehling’s solution?
Due to the ethanal acting as a reducing agent with reduces Cu₂+(blue) → Cu+ (red)
What is the equation for the reaction of ethanal with Fehling’s solution?
CH₃CHO + CU(₂+) → CH₃COOH + Cu+
What colour is CH3CHO?
Colourless
Name for CH3CHO
Acetaldehyde
What gets oxidised in the reaction of ethanal with Fehling’s solution?
Ethanal
What does ethanal get oxidised to in the reaction of ethanal with Fehling’s solution?
Ethanoic acid
What are the steps in the reaction of ethanal with Tollen’s Reagent?
- Place a few cm3 of silver nitrate solution into a test tube. Add a small amount of NaOH
- Add a few drops of ammonia until the silver oxide pt disappears.
- Add a few drops of ethanal and warm gently
What is the result in the reaction of ethanal with Fehling’s solution?
A deposit of metallic silver is seen on the inside of the test tube.
Why is a deposit of metallic silver seen on the inside of the test tube in the reaction of ethanal with Fehling’s solution?
Due to the silver in Tollens Reagent which has an oxidisation number of Ag(+1) being reduced by ethanal to metallic silver which has an oxidation number of Ag(0).
What is the equation in the reaction of ethanal with Fehling’s solution?
CH₃CHO + Ag(+) → CH₃COOH + Ag(↓)
What is used to produce an aldehyde?
A primary alcohol
What would happen if we were to oxidise a secondary alcohol such as propan-2-ol in a similar manner to producing an aldehyde?
We would produce a corresponding ketone, propanone.
Are ketones easily oxidised to become the carboxylic acid?
No
Is it necessary to use the same precautions i.e an excess of alcohol over oxidising agent with ketones and explain why?
No as ketones are not easily oxidised
What happens in the reduction of aldehydes?
Aldehydes are reduced to the primary alcohol using hydrogen and a nickel catalyst.
What is the equation for the reduction of aldehydes?
CH₃CHO + H₂ → C₂H5OH
What happens in the reduction of ketones?
Ketones are reduced to the secondary alcohol using hydrogen and a nickel catalyst.
Nickel (catalyst) ‘symbol’
Ni
Equation for the reduction of ketones.
CH₃COCH₃ + H₂ → CH₃CH(OH)CH₃
Short description of sodium carbonate.
White powder
What are the steps in the reaction of ethanoic acid with sodim carbonate?
- A spatula load of sodium carbonate was placed into a test tube.
- A few cm3 of ethanoic acid was added
What was the result in the reaction of ethanoic acid with sodim carbonate?
Effervescence was observed as carbon dioxide was given off. This carbon dioxide quenched a lighted taper held at the mouth of the test tube.
Equation for the reaction of ethanoic acid with sodium carbonate.
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + CO₂ +H₂0
Briefly describe magneisiam metal
Silver, burns with a bright light
Steps in the reaction of ethanoic acid with magneisiam metal.
- A test tube was quarter filled with ethanoic acid.
- About 3cm of masgneisiam ribbon was added.
Result of the reaction of ethanoic acid with magneisiam metal.
The magneisiam ribbon disappeared and hydrogen gas was given off.
Equation for the reaction of ethanoic acid with magneisiam metal.
2CH₃COOH +Mg → (CH₃COO)₂Mg +H₂
Magneisiam ethanoate molecular formula
(CH₃COO)2Mg
Which reaction is referred to as an esterification reaction?
The reaction of ethanoic acid with ethanol
What can the reaction of ethanoic acid with ethanol be called other then an esterification reaction?
A substitution reaction
Why can the reaction of ethanoic acid with ethanol also be called a substitution reaction?
As the hydrogen of the -OH group of acid is replaced by an alkyl group from an alcohol.
What can the reaction of ethanoic acid with ethanol be called other than an esterification reaction and a substitution reaction?
A condensation reaction.
Why can the reaction of ethanoic acid with ethanol be called a condensation reaction?
As two different molecules react to produce a more complex molecule with the production of a smaller molecule such as water.
What happens when ethanoic acid and ethanol are refluxed together?
The ester ethyl ethanoate is formed.
What happens in the reaction of ethanoic acid with ethanol?
A carboxylic acid and an alcohol are reacted together under reflux in the presence of concentrated sulfuric acid.
What is the purpose of the concentrated sulfuric acid in the equation : CH₃COOH + C₂H₅OH ⇋ CH₃COOC₂H₅ + H₂O
- Acts as a dehydrating agent and a catalyst
What does the dehydrating agent (concentrated sulfuric acid) in the equation : CH₃COOH + C₂H₅OH ⇋ CH₃COOC₂H₅ + H₂O cause?
Causes the water concentration to decrease which drives the position of equilibrium to the right, favouring the forward reaction so more ester, ethyl ethanoate is produced.
What are carboxylic acids reduced to first in the reduction of carboxylic acids?
An aldehyde
What are carboxylic acids reduced to after firstly being reduced to an aldehyde?
A primary alcohol
What is used to reduce carboxylic acids to firstly an aldehyde then a primary alcohol? (reduction of carboxylic acids)
Using hydrogen and a nickel catalyst.
What is the equation for the reduction of carboxylic acids?
CH₃COOH + H₂ → CH₃CHO + H₂ → C₂H₅OH
CH₃COOH + H₂ → CH₃CHO + H₂ → C₂H₅OH Name the condition and the reagent.
Condition = Nickel catalyst Reagent = H₂
Draw the funtional group of aldehydes. (L.C)
In notes
Draw the functional group of carboxylic acids. (L.C)
In notes
What is an ester? (L.C)
A compound formed when the hydrogen of the functional group of a carboxylic acid is replaced by an alkyl radical of an alcohol.
Give the two functions of using concentrated sulfuric acid in an esterification reaction. (L.C)
- As a catalyst
- As a dehydrating agent
Name the following molecule, CH₃CHBrCHO. (L.C)
n
Which of the following has a higher boiling point, CH₃CHO or CH₃COOH. Explain your reasoning. (L.C)
n
How many tetrahedral carbons would you find in ethyl methanoate? (L.C)
n
What is meant by a condensation reaction? (L.C)
Occurs when two different moleculescombine to form a more complex molecule with the production of a smaller molecule such as H₂0.
Draw and name the final product produced by the reduction of butanone. Identify the reagent used in this reaction. (L.C)
n
Classify the following alcohols - propan-2-ol, butan-1-ol. (L.C)
n
A sample of ethanoic acid (CH₃COOH) was prepared by the oxidation of ethanol. Describe and explain the colour change observed in the reaction flask as the ethanol was oxidised. (L.C)
- Orange to green
- dicromate reduced to chromium
Reflux is a widely used technique in organic chemistry. Identify an experiment from your course where you refluxed a mixture. Draw a fully labeled diagram of the reflux apparatus used in this experiment. (L.C)
- Preparation of soap Draw : Flask with contents shown or labeled - Anti-bumping granules - condenser in correct position - Labelled source of heat.
Reflux is a widely used technique in organic chemistry. Identify an experiment from your course where you refluxed a mixture. What happened to the liquid in the flask during reflux? (L.C)
- Liquid evaporated / hot vapour rose
Reflux is a widely used technique in organic chemistry. Identify an experiment from your course where you refluxed a mixture. How did refluxing this mixture help bring the reaction to completion? (L.C)
Allowed enough time to bring reaction to completion.
A sample of ethanoic acid (CH₃COOH) was prepared by the oxidation of ethanol. Describe your observations when a small quantity of solid sodium carbonate was added to a sample of the ethanoic acid produced. Write a balanced chemical equation for the reaction which occured. (L.C)
- Effervescence / gas given off
- Na₂CO₃ + 2CH₃COOH → 2CH₃COONa + H₂0 + CO₂
Alcohol X ⇋ Aldehyde Y ⇋ Carboxylic acid Z
Name X,Y and Z (L.C)
X = Ethanol Y = Ethanal Z = Ethanoic acid
Give a major use for ethanoic acid. (L.C)
As a flavouring agent
Draw the structure of ethanal, showing the boding between the atoms. (L.C)
In notes
What ester is formed from ethanol and ethanal? (L.C)
Ethylethanoate
Give two reasons why alcohols have a higher boiling point than corresponding alkanes. (L.C)
- Alcohols have higher relative molecular mass
- Intermolecular hydrogen bonds
Explain why the difference in boiling points between methane and methanol is 226.5K while the difference in boiling points between butane and butanol is only 119K. (L.C)
Due to a longer carbon chain / hydrogen bonding is weaker in butanol.
Describe in general terms, the solubilities of methane and methanol, butane and butanol in water. (L.C)
Methane - virtually insoluble
Methanol - compleatly soluble
Butane - virtually insoluble
Butanol - slightly soluble
A group of students prepared ethanal by slowly adding an aqueous solution of ethanol and sodium dichromate to a hot aquous solution of sulfuric acid. Why was the receiving vessel cooled in ice-water? (L.C)
- Volatile product / ethanal has low b.p
A group of students prepared ethanal by slowly adding an aqueous solution of ethanol and sodium dichromate to a hot aquous solution of sulfuric acid. State 2 features of the preparation that are necessary to maximise the yield of ethanal and for each feature, explain. (L.C)
- Excess ethanol - so it doesn’t go to ethanoic acid
2. Dichromate in funnel - small amount of oxidising agent in flask
A group of students prepared ethanal by slowly adding an aqueous solution of ethanol and sodium dichromate to a hot aquous solution of sulfuric acid. Describe and account for the colour change which is observed during the addition of ethanol and sodium dichromate solution to the hot acid. (L.C)
Describe - Orange solution added to colourless solution turns green
Account - Cr(VI) is reduced to Cr(III)
A group of students prepared ethanal by slowly adding an aqueous solution of ethanol and sodium dichromate to a hot aquous solution of sulfuric acid. Describe how you would carry out Fehling’s test on a sample of ethanal. What observation would you expect to make in this test? (L.C)
Test - Mix equal amounts of Fehling’s 1 and Fehling’s 2 and add ethanal and warm
Observe - Brick-red → precipitate produced
