Module 4 Flashcards
What does nomenclature mean?
The system used for naming organic compounds
What does the term empirical formula mean?
Simplest whole number ratio of atoms in a molecule
What does the term molecular formula mean?
It provides the actual number of atoms of different elements in a molecule
What does the term displayed formula mean?
It shows every atom & every bond in a molecule
What does the term structural formula mean?
It shows the arrangement of atoms in a molecule without showing every bond.
Define skeletal formula
A type of formula which is drawn as lines with each vertex being a carbon atom. Carbon atoms not drawn, assumed each C atom has all unspecified bonds as C-H
Define homologous series
A series of organic compounds having the same functional group but with each successive member differing by CH2
What is a functional group
A group of atoms responsible for characteristic reactions of a compound
What is an aliphatic hydrocarbon
Hydrocarbon with carbon atoms joined together in a straight line or branched chain
What is alicyclic hydrocarbon
Hydrocarbons arranged in non aromatic rings with or without side chains
What is an aromatic hydrocarbon
Hydrocarbon that contains at least one benzene ring
Give the suffixes for:
a) no double bonds
b) at least one double bond
c) an alcohol
d) an aldehyde
e) a ketone
f) a carboxylic acid
a) no double bonds = -ane
b) at least one double bond = -ene
c) an alcohol = -ol
d) an aldehyde = -al
e) a ketone = -one
f) a carboxylic acid = -oic acid
Give the prefixes for:
a) CH3 group
b) C2H5 group
c) C3H7 group
d) C4H9 group
e) Cl group
f) Br group
g) I group
a) CH3 group = methyl-
b) C2H5 group = ethyl-
c) C3H7 group = propyl-
d) C4H9 group = butyl-
e) Cl group = chloro-
f) Br group = bromo-
g) I group = iodo-
What is the general formula of alkanes
Cn H2n+2
What is the general formula for alkenes
Cn H2n
What is the general formula of alcohols
Cn H2n+1 OH
What does saturated mean
Organic compounds which only contain single bonds
What are unsaturated compounds
Organic compounds that contain at least one carbon carbon double covalent bond
Define structural isomerism
When molecules have the same molecular formula but different structural formula
What are the 3 ways in which structural isomerism can be formed
- Alkyl groups can be in different places
- Functional groups can be bonded to different parts
- There can be different functional groups
What are stereoisomers
Organic compounds with the same molecular formula but have different arrangements of atoms in space
What is E/Z isomerism and how are the E and Z isomers decided
E/Z isomerism is caused by the limited rotation C=C double bonds
Of the two substituents with the highest atomic number are on the same side of the double bonds, it is the Z (zusammen) isomer
If they are on different sides, it is the E (entgegen) isomer
What is a Cis-trans isomerism?
Special type of E/Z isomerism where the two substituents on each carbon atom are the same
What is a homolytic fission
It happens when each bonding atom revives one electron from the bonded pair forming two radicals
What is heterolytic fission
When one bonding atom receives both electrons from the bonded pair
What are radicals
Highly reactive, neutral species
How is a covalent bond formed from two radicals
The radicals collide and two unpaired electrons come together and a covalent bond forms
What is an alkane
A saturated hydrocarbons containing C-H bonds only
Are alkanes bonds polar? Why/why not
Non-polar because Carbon & hydrogen have similar electronegativity
What is the shape & angle of an alkane
Tetrahedral.
109.5 degrees
Describe the sigma bond in alkanes
The sigma bond is a covalent bond which has a direct overlap of the electrons orbitals of the bonding atoms
What type of intermolecular forces do alkane have? Why?
London forces → induced dipole-dipole interaction, because the bonds are non polar
What happens to the boiling point as alkane chain length increases? Why?
Boiling point increases, because more surface area & so more number of induced dipole-dipole interaction. More energy required to overcome attraction
Does branched molecule have lower or higher boiling point compared to equivalent straight chain? Why?
Branched molecule has lower boiling because fewer surface area & hence less induced dipole-dipole interactions.
Are alkanes soluble in water?
Insoluble because hydrogen bonds in water are stronger than alkanes’ London forces of attraction
How reactive are alkanes?
Very unreactive
What reactions will alkanes undergo?
Combustion & reaction with halogens
What type of reaction is combustion?
Oxidation reaction
What is complete combustion?
Combustion that occurs with plentiful supply of oxygen
What are the products of complete combustion when alkanes are used?
Carbon dioxide & water
What is the colour of the Bunsen burner flame during complete combustion?
Blue flame
What is incomplete combustion and what products are formed in the case of alkanes?
Combustion in a limited supply of oxygen
Products: water, carbon dioxide & carbon monoxide
Write an equation for the combustion of propane
C3H8 + 5O2 → 3CO2 + 4H2O
What type of hydrocarbon are most likely to undergo incomplete combustion?
Longer chains
What is the environmental impact of carbon monoxide?
Toxic / poisonous
What is the emironmental impact of soot (carbon)
Asthma, cancer, global dimming
How are halogenoalkanes formed from alkanes?
Radical substitution
What are the 3 stages of free radical substitution?
Initiation = breaking halogen bond to form free radicals
Propagation = chain part of the reaction where products are formed but free radical remains.
Termination = free radicals removed, stable products formed.
Write equation for the reaction of CH4 with CI2 to form CH3Cl
Initiation = Cl2 → 2Cl• ( in presence of UV light)
Propagation = CI• + CH4→ HCl + •CH3
•CH3 + Cl 2 → CH3Cl + CI•
Termination = •CH3 + Cl• → CH3Cl
2Cl• → Cl2
•CH3 + •CH3 → CH3CH3
What are alkanes
Unsaturated hydrocarbons that contain at least one C=C bond made up of a pi-bond & a sigma-bond
How is a pi-bond formed?
Electrons in the adjacent P orbitals overlap above & below the carbon atoms. They can only be made after a sigma-bond is formed.
What bond restricts the rotation of carbon atoms?
Pi bonds because of the electron overlap both above and below the plane of the atoms
What is the angle & shape of a double bond
trigonal planar
120 degrees
Are alkenes more or less reactive than alkanes? Why?
More reactive due to high electron density of double bond & the fact the pi-bond is slightly easier to break
What intermolecular forces of attraction do alkanes have?
Only London forces due to non-polar bonds
Are alkanes soluble in water?
No, they have non-polar bonds
What are the types of isomers that can be formed using alkanes?
E/Z isomers - due to the restricted rotation
Cis-trans isomers - if 2 of the same substituents are attached to each carbon
What is an electrophile?
Species that are electron pair acceptors
What is the most stable type of carbocation intermediate? Why?
Alkyl groups have a positive inductive effect, so the most stable carbocation is the one bonded to the most other carbon atoms ie A tertiary carbocation
Major products will be formed from which kinds of carbocations?
Tertiary ( or the most stable available)
What conditions are needed for the elechophilic addition of H2O to an alkene?
Steam in the presence of an acid catalyst, usually phosphoric acid
Reaction is called hydration
What are the product of the hydration reaction?
In alcohol
What conditions are needed for the electrophilic addition of a hydrogen halide to an alkene?
Hydrogen halide gases must be at room temp.
What is the name of the reaction when a halogen is added to alkene?
Halogenation
How does A molecule with a non-polar bond react as if it is an electrophile?
C=C double bond with a high electron density induces a temporary dipole in the halogen molecule → + atom attracted to double bond
How can on alkene be converted into alkane?
Alkene + hydrogen = alkane
Hydrogenation
Conditions → 150 degrees, nickel catalyst
What is an addition polymer
Many monomers bonded together via rearrangement of bonds without the loss of any atom or molecule
What are monomers? What form do they usually take?
Molecules which combine to form a polymer
Usually have A C=C bond which breaks to leave a repeating pattern
General Formula of Alcohols
- Alcohols have the general formula CₙH₂ₙ₊₁OH
- Contain the hydroxyl (-OH) functional group
- Homologous series with similar chemical properties but increasing molecular size
Classification of Alcohols
- Primary alcohol (1°)
→ OH group attached to a carbon bonded to one alkyl group
→ Example: Ethanol (CH₃CH₂OH) - Secondary alcohol (2°)
→ OH group attached to a carbon bonded to two alkyl groups
→ Example: Propan-2-ol (CH₃CHOHCH₃) - Tertiary alcohol (3°)
→ OH group attached to a carbon bonded to three alkyl groups
→ Example: 2-methylpropan-2-ol (CH₃)₃COH
Physical Properties of Alcohols
- Boiling Points:
→ Higher than corresponding alkanes due to hydrogen bonding
→ As chain length increases, boiling point increases - Solubility in Water:
→ Short-chain alcohols (e.g., methanol, ethanol) are soluble due to hydrogen bonding
→ long -chain alcohols are less soluble because the non-polar hydrocarbon chain dominates
Combustion of Alcohols
- Alcohols combust in oxygen to form carbon dioxide and water
- Complete combustion (excess oxygen):
→ Example: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O - Incomplete combustion (limited oxygen):
→ Produces carbon monoxide (CO) or carbon (C)
Oxidation of alcohols
- Oxidizing agent: Acidified potassium dichromate (K₂Cr₂O₇/H₂SO₄)
- Color change: Orange → Green when oxidation occurs
- Primary Alcohols (1°) Oxidation
→ Partial oxidation (forms aldehyde)
→ Distillation used to remove aldehyde (prevents further oxidation)
→ Example: Ethanol → Ethanal
→ CH₃CH₂OH + [O] → CH₃CHO + H₂O
→ Full oxidation (forms carboxylic acid)
→ Reflux to ensure complete oxidation
→ Example: Ethanol → Ethanoic acid
→ CH₃CH₂OH + 2[O] → CH₃COOH + H₂O - Secondary Alcohols (2°) Oxidation
→ Forms ketones
→ Requires reflux with acidified potassium dichromate
→ Example: Propan-2-ol → Propanone
→ CH₃CHOHCH₃ + [O] → CH₃COCH₃ + H₂O - Tertiary Alcohols (3°) Oxidation
→ Do not oxidize because there is no hydrogen on the carbon bonded to -OH
→ Remain orange in potassium dichromate test
Dehydration of Alcohols (Elimination Reaction)
→ Alcohol → Alkene + Water
→ Uses concentrated H₂SO₄ or H₃PO₄ as a catalyst
→ Reaction occurs under reflux
→ Example: Ethanol → Ethene + Water
→ CH₃CH₂OH → CH₂= CH₂ + H₂O
Conversion of alcohols to haloalkanes
- Alcohols react with hydrogen halides (HBr, HCl, HI)
- Example: Ethanol + HBr → Bromoethane + Water
→ CH₃CH₂OH + HBr → CH₃CH₂Br + H₂O - Alternative method: Sodium halide (NaBr) + Sulfuric acid (H₂SO₄)
→ NaBr + H₂SO₄ → HBr (in situ)
→ HBr then reacts with alcohol to form a haloalkane
Testing for alcohols
- Oxidation test (Acidified potassium dichromate)
→ Primary/secondary alcohols: Orange → Green
→ Tertiary alcohols: No color change - Dehydration test:
→ Forms alkene, which decolorizes bromine water (Br₂) - Lucas test (ZnCl₂ + HCl):
→ Primary alcohols: No reaction
→ Secondary alcohols: Cloudiness after a few minutes
→ Tertiary alcohols: Immediate cloudiness
