Naming Organic Compounds
Name CH₃–CH₂–CH₃.
Answer: Propane.
Draw the complete structural formula of ethene.
Answer:
CH2=CH2
Is ethanol or long-chain alcohol more soluble in water?
Ethanol
Write the balanced complete combustion equation for methane and identify the reaction type.
Answer:
CH4 + 2O2 --> CO2 + 2H2O
Reaction type: Complete combustion.
Give two uses of alkanes and explain why their properties make them useful.
(answers may vary)
Answer:
1) Methane is used as a fuel for heating and electricity generation.
2) Longer-chain hydrocarbons are used in gasoline and other fuels.
Alkanes release energy during combustion and are relatively unreactive under ordinary conditions.
Name CH₃–CH(OH)–CH₃.
Answer: Propan-2-ol (2-propanol).
Give the condensed structural formula of but-1-yne
Answer:
HC≡C–CH₂–CH₃
Why do alkanes generally have lower boiling points than alcohols of similar molar mass?
LDF only, as opposed to alcohols's hydrogen bonding.
Write the reaction between ethene and bromine and identify the reaction type.
Answer:
CH2=CH2 + Br2 --> CH2BrCH2Br
Reaction type: Addition (halogenation). The double bond opens, allowing one bromine atom to attach to each carbon.
What are two uses of alkenes?
(answers may vary)
Answer:
1) Ethene is used to manufacture polyethylene plastic.
2) Ethene is used commercially to promote fruit ripening.
Their carbon–carbon double bonds allow addition reactions and polymerization.
Name CH₃–CO–CH₂–CH₃ and identify its functional group.
Answer: Butan-2-one; ketone.
Draw ethanoic acid
CH3COOH
Why do carboxylic acids often have higher boiling points than similar-sized alkanes, and what happens to their acidity in water?
Answer: Carboxylic acids form hydrogen bonds and can form hydrogen-bonded dimers, raising their boiling points. In water, they partially ionize, transferring a proton to water and forming hydronium ions (H₃O⁺).
Show the oxidation of a primary alcohol to an aldehyde and then a carboxylic acid.
Answer:
RCH2OH + [O] --> RCHO + H2O
RCHO + [O] --> RCOOH
Reaction type: Oxidation. A primary alcohol can form an aldehyde under controlled conditions and a carboxylic acid with further oxidation.
Identify two applications of amines and explain the role of their chemistry.
(answers may vary)
Answer:
1) Pharmaceutical manufacturing.
2) Production of dyes and other industrial chemicals.
The nitrogen atom can act as a base and participate in reactions that help build more complex molecules.
Name CH₃–CH₂–CHO and CH₃–CH₂–NH₂.
Answer: Propanal and ethanamine.
Draw a repeating unit of polyethylene. Circle the monomer
...[-CH2-CH2-]CH2-CH2-
Compare the intermolecular forces and boiling points of an alcohol and an ether with similar molar masses.
Answer: Both have London dispersion forces and, if polar, dipole–dipole attractions. Alcohols also hydrogen-bond to each other, so they usually have higher boiling points than comparable ethers.
Write the esterification reaction between ethanoic acid and ethanol.
Answer:
CH3COOH + CH3CH2OH -><- CH3COOCH2CH3 + H2O
Products: Ethyl ethanoate and water.
Reaction type: Esterification, a condensation reaction. An acid catalyst and heat are commonly used.
Give one use each for esters, ethers, aldehydes and ketones.
(answers may vary)
Answer:
1) Esters: Fragrances and flavourings, because many have pleasant or fruity odours.
2) Ethers: Solvents in chemical and industrial processes.
3) Aldehydes: Manufacture of resins and other chemicals.
4) Ketones: Acetone is used as a solvent, including in some nail-polish removers.
Name CH₃CONH₂ and identify the functional group in CH₃COOH.
Ethanamide (acetamide); the second compound contains a carboxylic acid group (–COOH).
Draw the structural formula for Methyl Methanoate
H-COO-CH3
Compare small amides with alkanes in terms of solubility and boiling point.
Answer: Small amides are generally more polar and often more water-soluble than alkanes. Amides have strong dipole–dipole attractions, and many can form hydrogen bonds. These stronger intermolecular forces generally lead to higher melting and boiling points.
Write the polymerization equation for ethene and explain how amides can form from carboxylic acids and amines.
Answer:
nCH2=CH2 --> [-CH2 - CH2-]n
Reaction type: Addition polymerization.
In a simplified condensation reaction, a carboxylic acid and an amine can form an amide linkage with loss of water. Actual reactions may require particular conditions because direct combination is not always straightforward.
Give two applications of amides and two applications of polymers. Explain how their structures support their uses.
(answers may vary)
Answer:
1) Amides: Proteins contain peptide (amide) bonds; nylon contains amide linkages and is used in textiles and fibres.
2) Polymers: Polyethylene is used in packaging; PVC is used in pipes and cable insulation.
Strong covalent bonds along polymer chains provide durability, while chain arrangement, intermolecular attractions and additives influence flexibility, strength and heat resistance.