CHE 176-Organic Chemistry 1 Quiz on Hydrocarbons

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Questions and Answers

What is the general formula for alkanes?

CnHn

CnH2n

CnH2n-2

CnH2n+2 (correct)

Which of the following statements is true about aliphatic hydrocarbons?

They include only cyclic compounds.

They possess double and triple bonds.

They are all aromatic compounds.

They contain carbon and hydrogen atoms. (correct)

Which classification does NOT belong to aliphatic hydrocarbons?

Alkynes

Alkenes

Alkanes

Aromatic hydrocarbons (correct)

What distinguishes alkanes from alkenes and alkynes?

Alkanes do not possess double or triple bonds. Signup and view all the answers

Which of the following statements about the IUPAC rules is correct?

IUPAC rules evolved from various international conferences. Signup and view all the answers

What is the primary product of the cracking process?

Smaller alkanes and alkenes Signup and view all the answers

What undesirable effect does sulfur have on petrol combustion?

Deactivates tetraethyl lead Signup and view all the answers

What does the octane number of petrol indicate?

The percentage of isooctane in the fuel Signup and view all the answers

Which of the following is a consequence of adding tetraethyl lead to petrol?

Increases pollution Signup and view all the answers

What is the origin of petroleum according to the outlined process?

Dead marine organisms Signup and view all the answers

What is the main reason for synthesizing alkanes above n-pentane?

The number of isomers becomes large and boiling point differences small Signup and view all the answers

What is knocking in the context of internal combustion engines?

Burning of residual fuel that causes metallic sounds Signup and view all the answers

What role does temperature and pressure play in the formation of hydrocarbons?

They lead to decomposition and maturation of organic compounds Signup and view all the answers

What is the primary role of the catalyst in the hydrogenation of alkenes?

To lower the energy of activation Signup and view all the answers

What is produced when Grignard Reagent reacts with water?

An alkane Signup and view all the answers

In the reduction of alkyl halides using zinc and acid, what is formed along with the alkane?

A metal halide Signup and view all the answers

Which of the following statements is true regarding hydrogenation reactions?

They convert alkenes to alkanes quantitatively. Signup and view all the answers

What is produced when alkanes react with chlorine or bromine under UV light?

Chloroalkanes or bromoalkanes Signup and view all the answers

Why is the volume of hydrogen consumed during hydrogenation important?

It can be used to determine the number of double bonds. Signup and view all the answers

Which of the following occurs during the reaction of an alkyl halide with a Grignard reagent?

Replacement of halogen with H Signup and view all the answers

What happens to the reaction rate of hydrogenation in the absence of a catalyst?

It proceeds at a negligible rate. Signup and view all the answers

What is the primary component of natural gas?

Methane Signup and view all the answers

Which fraction of petroleum constitutes the largest percentage of daily consumption?

Gasoline Signup and view all the answers

At what boiling point range does kerosene typically exist?

180°C to 230°C Signup and view all the answers

What is the use of lubricants derived from petroleum?

Paraffin wax and petroleum jelly Signup and view all the answers

Which fraction of petroleum is primarily used as jet fuel?

Kerosene Signup and view all the answers

What is the main purpose of distillation residues like asphalt?

Roofing and road building material Signup and view all the answers

Which petroleum fraction has a boiling point range of 230°C to 305°C?

Light gas oil Signup and view all the answers

Which of the following statements about saturated hydrocarbons is true?

They are stable in the presence of reducing agents at ordinary temperatures. Signup and view all the answers

What is the formula for butane?

C4H10 Signup and view all the answers

Which of the following represents the correct name for the hydrocarbon CH3-CH2-CH(CH3)-CH3?

2-methyl butane Signup and view all the answers

Which prefix indicates the presence of three substituents?

tri- Signup and view all the answers

In naming branched chain hydrocarbons, what is the basis for determining the parent hydrocarbon?

The longest continuous chain of carbon atoms Signup and view all the answers

How should the chain be numbered in a branched-chain alkane to give the lowest possible numbers to the substituents?

From the end nearest a substituent Signup and view all the answers

Which of the following compounds is incorrectly named based on IUPAC nomenclature rules?

3,4-dimethylpentane Signup and view all the answers

What is the chemical formula for nonane?

C9H20 Signup and view all the answers

Which of these alkanes has the molecular formula CH3(CH2)9CH3?

Undecane Signup and view all the answers

What is the correct order for naming alkyl groups when multiple are attached to a parent chain?

In increasing size or alphabetical order Signup and view all the answers

How does the boiling point of alkanes change as the number of carbon atoms increases?

Increases consistently due to added CH2 groups Signup and view all the answers

What defines a homologous series in chemistry?

Compounds differing by a specific number of atoms Signup and view all the answers

What can be predicted about the boiling point of octane based on the boiling points of hexane and heptane?

It will be approximately 127 °C Signup and view all the answers

Why are alkanes referred to as saturated hydrocarbons?

Their chemical affinity with reagents is maximized Signup and view all the answers

What is the estimated boiling point of octane if the boiling point of heptane is known to be 98 °C?

127 °C Signup and view all the answers

Which property of alkanes is affected the least by increasing carbon chain length?

Chemical reactivity Signup and view all the answers

In the structural representation CH3-CH2-CH2-CH2-CH2-CH2-CH3, how is the heptane structured?

It is a straight-chain structure Signup and view all the answers

Study Notes

Course Information

Course title: CHE 176-Organic Chemistry 1
Course subtitle: Basic Concepts of Organic Chemistry
Instructor: Dr. Ganiyat K. Oloyede
Office: B18, Department of Chemistry
Course lecturers (2020/2021): Prof. O. O. Sonibare, Dr. Ganiyat K. Oloyede, Dr. Dorcas O. Moronkola, Dr. Sherifat A. Aboaba
Course outline: Check the faculty prospectus
Lecture outline (Dr.G. K. Oloyede): Synthesis, reactions, and uses of alkanes including petroleum, alkenes, alkynes, and aromatic compounds; haloalkanes.

Hydrocarbons

Organic compounds containing only carbon (C) and hydrogen (H) are called hydrocarbons.
Hydrocarbons are categorized into two main classes: aliphatic and aromatic.
Aliphatic hydrocarbons are further divided into alkanes, alkenes, alkynes, and their cyclic analogues (viz.).

IUPAC Nomenclature for Alkanes

Alkanes are compounds of C and H that don't have double or triple bonds, or rings. The general formula is CnH2n+2.
The most definitive set of organic nomenclature rules currently in use. (Known as International Union of Pure and Applied Chemistry Rules or IUPAC rules)
The old trivial names derived from possible sources of the organic compounds (e.g. acetic acid or formic acid) are gradually being discarded.
Nomenclature is based on the longest continuous chain of carbon atoms (in straight/continuous chains)
The carbons are numbered to give the lowest numbers to the side chains/substituents (branched chains)
Prefixes are used to designate the number of substituents (1-mono, 2-di, 3-tri, 4-tetra, 5-penta, etc.)

Physical Properties of Alkanes

The series of straight-chain alkanes shows a remarkably smooth graduation of physical properties.
Each additional CH₂ group contributes a fairly constant increment to the boiling point and density, and to a lesser extent, the melting point (homology).
The properties of unknown members of the series can be estimated from those of its neighbours.
For example; Hexane (69°C) and heptane (98°C), one CH₂ group difference = 29°C).
Alkanes are usually unreactive (saturated) thus, their bonds are satisfied with ordinary temperatures or ordinary conditions

Petroleum and its Fractions

Alkanes are a major component of petroleum.
Petroleum from distillation yields various fractions: gas fraction (C₁-C₅), gasoline (C₆-C₁₀), kerosene (C₁₁-C₁₂), light gas oil (C₁₃-C₁₇), heavy gas oil and light lubricating distillate (C₂₆-C₃₅), lubricants.
Daily use percentages for each fraction are given, eg. gasoline is 39%.
Petroleum fractions are used as fuels for various applications (heat and power), industrial power plants, and transportation.
Petroleum's origin is from dead marine organisms buried deep in sedimentary rock, (millions of years) during decomposition, and then maturation into hydrocarbons.
Cracking and isomerization processes process the petroleum.
Sulphur is usually an undesirable component of petroleum.
Properties of petroleum are measured/classified by octane rating
- 2,2,4-trimethylpentane is the standard for good anti knock behaviour (100)
Octane number refers to percentage isooctane (high-octane fuel)

Chemical Reactions of Alkanes

Alkanes are generally unreactive because their bonds are generally saturated -Under the influence of ultraviolet light, Chlorine or Bromine can convert the alkanes into chloroalkanes or bromoalkanes.
Alkanes can undergo complete combustion with oxygen at high temp to form CO₂ and H₂0
Alkanes, in vapour phase, can undergo nitration.
Alkanes undergo sulphonation to form sulphonic acid

Important Methods for Alkane Preparation

Hydrogenation (general formula: CnH2n + H₂ = CnH2n+2): The most important method for preparing alkanes. Alkenes + hydrogen under slight pressure and in the presence of a catalyst convert to alkanes.
Reduction by metal and acid.
Hydrolysis of an alkyl halide

Analytical Tool for Alkanes (Hydrogenation)

Hydrogen required to saturate an alkene gives an indication of the no. of double or triple bonds in a molecule.
Hydrogenation is an exothermic reaction, and the volume of H₂ consumed can be easily measured.

Mechanisms of Halogenations of Alkanes

Halogenation of alkanes occurs via a chain reaction mechanism involving homolytic cleavage (radical formation).
- Initiation, Propagation, Termination

Further Information regarding Chemistry of Alkanes.

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Description

This quiz assesses your understanding of hydrocarbons, focusing on their classification into aliphatic and aromatic compounds. You'll also explore IUPAC nomenclature for alkanes, including their structure, reactions, and uses. Prepare to demonstrate your knowledge of these fundamental concepts in organic chemistry.