Flashcards in Organic Compounds Deck (142):
How is methane produced?
By anaerobic bacterial decomposition of either animal waste or vegetation
Why is the concentration of methane a cause of concern?
The boiling points of propane and dodecane are -42 and 216 respectively. Explain why high molecular mass alkanes have high boiling points?
Stronger intermolecular bonds
Distinguish between saturated and unsaturated hydrocarbons
Saturated hydrocarbons - only single bonds - has max no of hydrogens atom can have
Unsaturated - contains at least one double/triple bond, doesn't have max amount of hydrogens
How many pi electrons are there in benzene?
What is the distribution of pi electrons like in benzene?
Give evidence to support the fact that pi electrons are delocalised in benzene molecule
All c-c bonds are of same energy/length
All c-c bonds in benzene are intermediate between single and double in energy
What is organic chemistry?
Study of compounds of carbon other than carbon monoxide, carbon dioxide, carbonates and hydrogencarbonates]
What is a functional group?
It's an atom or group of atoms which is responsible for the characteristic properties of a series of organic compounds
What kind of bonds do saturated organic compounds have?
Sigma, end on overlap of atomic orbitals
What kind of bonding do unsaturated compounds have?
1 sigma with other bonds of pi type - sideways overlap of p orbitals
What are hydrocarbons?
Compounds that contain carbon and hydrogen only
What is a homologous series?
A family of organic compounds with the same general formula, similar chemical properties and successive members differing by CH2
What hydrocarbon when exposed to air forms an explosive mixture?
How are hydrocarbons formed?
They are naturally occurring and have been formed in the earth over millions of years, eg crude oil
What is the bond angle of a tetrahedral shaped molecule?
What are the three types of tetrahedral carbon compounds?
Alkanes, alcohols and chloroalkanes
What hydrocarbons are saturated?
The ones that contain single bonds - alcohol, alkanes and chloroalkanes
What is the functional group of alkanes?
carbon single bonds
What sort of reactions do alkanes undergo?
Give two uses of alkanes
Petrol - 5-10 atoms c atoms
Kerosene [jet due, and central heating fuel]
LPG [liquefied petroleum gas] made up of propane and butane
What are isomers?
Compounds with the same molecular formula but different structural formula
How do isomers differ?
Physical properties eg, boiling points
What is an alkyl group?
It's an alkanes molecule from which a hydrogen atom has been removed
CH3 - methyl
C2H5 - ethyl
What are alcohols?
Similar to alkanes but with a hydrogen replaced by OH
What is the functional group of alcohols?
How do you write molecular formula of alcohols?
Alkyl group + OH
What is a primary alcohol and give an example
When the carbon attached to the hydroxyl group is attached to one other carbon
What are secondary alcohols?
When the carbon attached to the hydroxyl group is attached to two other carbons
What are tertiary alcohols?
When the carbon attached to the hydroxyl group touches three other carbons
What must you always do when naming alcohols?
Indicate position of hydroxyl group
What changes alcohols chemistry drastically from corresponding alkanes?
Boiling point of alcohols?
Higher than corresponding alkanes
The hydroxyl undergoes hydrogen bonding which results in them having very strong bonds. As a result, it takes more energy to break apart bonds = higher
Solubility of alcohols?
It changes as length of carbon chain increases. The OH group is highly polar and if the chain is short, it forces the non polar part [alkyl group] to dissolve in polar substances such as water. If chain becomes too long, the OH group is insignificant and therefore dissolves in non polar substances instead
What shape is the functional group of alcohols?
Fruits with glucose have yeast added to them which contains catalyst zymase. Zymase converts glucose into ethanol and carbon dioxide as a result.
Why does fermentation alone not produce drinks greater than 12% v/v
Once ethanol reaches this percentage, it kills yeast - stops fermentation
How do you increase alcohol concentration and give an example
Fermented liquids are distilled eg, wine is distilled to brandy
What are the uses of ethanol?
Alcoholic drink [consumption], solvent [perfumes]
Why is ethanol a good solvent?
Due to hydrogen bonding
Describe hydrogen bonding in alcohols
Oxygen - partial negative charge [more electronegative]
Hydrogen - partial negative charge
Oxygen in hydroxyl group in one molecule attracts hydrogen in hydroxyl group on neighbouring molecule
This forms strong hydrogen bonds
Why do ethanol and water mix completely in alcoholic drinks?
Hydrogen bonds form between hydroxyl groups in ethanol and hydroxyl groups in water
What are chloroalkanes?
An alkane with one or more of its hydrogens replaced by chlorines
What's another name for chloroform and give a use
was used as an anaesthetic
Are chloroalkanes soluble in water?
No, carbon-chlorine bond is polar but not polar enough to make a different to physical properties
Boiling point in chloroalkanes
Low boiling points but higher than corresponding alkanes
What state are chloroalkanes in room temperature?
What two chloroalkanes are gases at room temp?
States at room temperature of alkanes
Up to C4 - gases
Next 12 - liquids
Rest - solids
Why does boiling point of chloroalkanes increase with carbon chain?
Stronger van der waals forces
Uses of chloroalkanes and why?
Used as solvents - lack of polarity, readily dissolve grease and oil which are insoluble in water
Give a damaging hydrocarbon in chloroalkanes
Chloromethane - damage to ozone layer
Name the carbon compounds that are planar
Alkenes, alkynes, aldehydes, ketones, carboxylic acids, esters, aromatic compounds
Shape of alkenes
Both tetrahedral and planar
Tetrahedral - everywhere but where double bond is
Are alkenes saturated or unsaturated?
Unsaturated - double bond
What reactions do alkenes undergo?
Uses of ethene
PVC - manufacturing of plastics
How is ethene prepared?
By dehydrating ethanol
How is ethanol prepared?
Shape of alkynes?
Both tetrahedral and planar
Tetrahedral - everywhere but where the triple bond is
Are alkynes unsaturated or saturated?
Unsaturated - triple bond
How is ethyne produced?
Water and calcium carbide bubbles through copper sulfate solution to get rid of impurities like phosphine, ammonia and hydrogen sulfide gas
What is aldehydes functional group and where is it positioned?
Carbonyl - CHO
At end of carbon chain
Boiling point of aldehydes
As carbonyl group contains dipole dipole forces they have a higher boiling than corresponding alkanes but a lower boiling point than their corresponding alcohols
First few aldehydes are soluble in water [polar] as dipole dipole forces can only force first few carbons to dissolve in a polar substance. Polar carbonyl group forces non polar alkyl group to dissolve however when the chains get longer, carbonyl polar becomes insignificant
H20 can form hydrogen bonds with carbonyl group = low chains
What state are most aldehydes in room temp?
Liquid except for methanal
Formula of methanal
Uses of aldehydes
Methanal in water = formalin and is used as an embalming fluid and to preserve biological specimens
What is benzaldehyde?
It's found in oil of almonds [kernels]
How to draw benzaldehyde
Normal benzene + CHO
Properties of ketones
Same as aldehydes
Difference between ketones and aldehydes?
The hydrogen atom in aldehydes is replaced by an alkyl group
Uses of ketones?
Organic solvent such as nail varnish remover
What is a carbonyl group?
Oxygen attached to a carbon atom by a polar double covalent bond
Carboxylic acid functional group?
Carboxyl = COOH
What are the intermolecular bonding present in carboxylic acids?
Hydrogen bonding = high boiling point as it takes a lot of energy to break them
Characteristics of carboxylic acids?
Unpleasant odours such as rancid butter and sweat
What are the bonds present in a carboxylic acids
Uses of carboxylic acids
Methanoic acid - stings of nettles and ants
Ethanoic acid - vinegar
Propanoic and benzoic - preserve foods
Why do carboxylic acids have higher boiling point than corresponding alcohol?
More hydrogen bonds between molecules
Carboxylic acids - solubility
Lower members are highly soluble in water due to carboxylic acid group forming hydrogen bonds with water molecule and decreases with length due to insoluble alkyl portion of molecule [polar group becomes insignificant]
State of matter of carboxylic acids at room temp?
Pure ethanoic acid - liquid but if it falls below 17 degrees it becomes solid = glacial acetic acid
What are dimers [carboxylic acid]
Groups of two molecules joined together
After carrying out the lab conversion of ethanol to ethene, how would you test the product to confirm the formation
Bromine water - test for unsaturation
Ethanol - Ethene conversion is a saturated [tetrahedral, single bonds] to unsaturated compound therefore if it is ethene, bromine water should go brown - colourless
Name the class of organic compounds that are responsible for the scent in fruits such as cherries
Three test tubes - ethanol, ethanoic acid and Eugenol but not in that order
It was observed that D evaporated more quickly that either C or E
What is D??
[weaker intramolecular forces]
Name the two acidic functional groups that occur in organic compounds
Complete the balanced equation -
C2H6 + Cl2 - uv light >
C2H6 + Cl2 - uv light > C2H5Cl + HCl
Explain in terms of bonding why it is more correct to represent the benzene molecule as (diagram of what it is)
Bonds intermediate between double and single bonds
All carbon-carbon bonds are identical
Name an ester that is a structural isomer of propanoic acid
Identify the reactant and transition metal catalyst used to reduce a ketone to an alcohol
Ester + HCOOH -> A -> ethene
-how does the geometry around the carbon atoms change in this conversion
Tetrahedral - planar
Explain the effect of the presence of tetraethyllead in substitution reaction between ethane and chlorine and ultraviolet light
Speeds up reaction as it provides ethyl radicals
What name is given to the type of reaction that occurs between sodium hydroxide and an ester
Name the addition polymer formed from propene
Identify the bonds broken and bonds formed in the conversion of propanone to propan-2-ol
Broken - CO pi bond
Formed - OH, CH
An isomer of propan-2-ol can be synthesised from an aldehyde. Name the isomer and the aldehyde
How can the aldehyde be converted to the isomer?
Isomer - propanol [primary alcohol]
Aldehyde - propanal
Be converted -> H2 + Ni catalyst
In the reaction between chlorine gas and ethane in the presence of UV light, explain how the occurrence of another hydrocarbon in the product mixture provides evidence for the mechanism
Combination of ethyl radicals forms butane
Identify the reagent to bring about C2H6 -> CH3CH2Cl
Identify the reagent to bring about C2H4 -> CH3CH2Cl
Identify the reagent required to bring about C2H4 -> CH2ClCH2Cl
Draw the structure of A and name when
CH2ClCH2Cl - HCL -> A
CH2 = CHCl
Draw the structure of two repeating units of PVC
H Cl H Cl
H H H H
What is the alcohol that forms from propanone is reduced
What is the structural difference between a primary and secondary alcohol
Primary - one carbon attached to OH
Secondary - two carbons attaches to OH
Identify an isomer of propanone
List the bonds broken and bonds form in the reaction of ethanol to ethene
Broken - C-O C-H
Formed - C=C C-H
Describe the bonding in benzene
Identical c-c sigma bonds
Delocalised pi bonds formed from six p orbitals
Sigma C-H bonds
State the reagents and conditions required to bring about
i ) C2H4 -> C2H6
ii ) C2H6 -> C2H5Cl
i ) H2
ii ) Cl2 + UV light
The conversion C2H4 -> PVC involves a three-step synthesis. Draw the structures of the two organic intermediates in this synthesis
H C=C H
Name the aromatic compound found in almond kernels that has the functional group of aldehydes
Which compound is formed as the primary metabolite of ethanol in the human body?
Describe what is observed when sodium carbonate is added to a test tube containing an aqueous solution of ethanoic acid
Fizzing and production of CO2, clear solution formed
Write a balanced equation for the addition of sodium carbonate to ethanoic acid
2CH3COOH + Na2CO3 -> 2CH3COONa + H20 + CO2
Express the concentration of a one molar solution of ethanoic acid in terms of % w/v
60g / 1000 x100/1 = 6%
The ionic addition mechanism for the reaction of ethene with bromine water involves the formation of an intermediate ionic species, what is it and be able to draw
Bromonium ion [show positive charge]
Give the names of the three products that would be formed if the bromine water used in the reaction contained sodium chloride and how does the formation of these three products support the mechanism of ionic addition
Different negative ions [Br-, OH-, Cl-] and water adding on indicates presence of positive intermediate. The formation of the products indicate the positive ion and negative ions added on
Name the polymer formed when ethene undergoes addition polymerisation. Draw two repeating units of this polymer
Name a suitable catalyst for the reduction reactions
How can alcohol be obtained?
Reduction of aldehydes and ketones using hydrogen and nickel
Name the alcohol produced when propanal is reduced
Give the name of the organic product of the oxidation of propanal in fehlings solution
Name two features of an elimination reaction
Removal of small molecule [H20]
Change to unsaturated molecule
List the bonds broken and bonds made in the synthesis of ethanal to ethanol
Broken - C-H + O-H
Made - C=O
An aldehyde is formed as a metabolite of an alcohol in the human body. How does the aldehyde come to be present in the body?
Ingestion [drink, food, medicine]
Give two reasons why alcohols have a higher boiling point than corresponding alkane
-higher molar 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 butanos is only 119K
Due to longer carbon chain, effect of OH is less [hydrogen bond is weaker]
State three clear pieces of experimental evidence which support the free radical substitution mechanism
reaction requires u.v. light of energy high enough to homolyse. For every photon absorbed very many (thousands of) molecules of a product are formed. if u.v is stopped the reaction slows down (stops)
products such as butane / chlorobutane / etc. formed
addition of radical promoters tetramethyl lead, tetra-ethyl lead) alter (speed up) the rate of the reaction
Name the compound C2H5Cl
What organic reaction type describes the esterification reaction from an alcohol and of a carboxylic acid
Give the name and structure of the intermediate organic compound in the synthesis of an alcohol to a carboxylic acid
Identify the type of organic reaction involved from an alcohol to a carboxylic acid
Identify the inorganic reagents which may be used in the oxidation reactions
How could the same product of hydrogen chloride and ethene be formed from ethane
Account for the greater reactivity of alkenes compared to allanes
Due to double bond -> electron rich and pi bonds are weak -> easier to react
What kind of a reaction is esterification?
What type of reaction is the one from ethene to ethane and give one use of this reaction in industry
Give one use for the group of compounds to which chloroethane belongs
Explain clearly the role of the ultraviolet light in the reacton between chlorine and methane
Provides energy for splitting of chlorine into free radicals
Name the two main products of the reaction between chlorine and methane
Account for traces of ethane found in product mixture of chlorine and methane
Methyl radicals combined to form ethane