Alkanes, Cycloalkanes, and Stereochemistry

This set of vocabulary flashcards covers concepts from the Alkanes, Cycloalkanes, and Stereochemistry lecture, including IUPAC nomenclature, physical properties, chemical tests, and spatial isomerism.

Alkanes

Hydrocarbons that contain carbon–carbon single bonds with the general formula $C_nH_{2n+2}$, where $n$ is the number of carbon atoms.

Paraffins

A name for alkanes derived from the Latin parum affinis, meaning "little affinity," referring to their low chemical reactivity.

Cycloalkanes

Alkanes in which the carbon atoms are arranged in a ring, having the general formula $C_nH_{2n}$ for single rings.

Petroleum

A complex mixture of organic compounds, primarily alkanes and aromatic compounds, which serves as the primary source of alkanes.

Distillation

The first step in refining petroleum, which separates the mixture into fractions based on the volatility of its components.

Catalytic cracking

The process of heating alkanes from the gas oil fraction (C12 and higher) at approximately $500\,^\circ C$ with catalysts to produce smaller, branched hydrocarbons ($C_5$–$C_{10}$).

Thermal cracking

The breakdown of hydrocarbons in the absence of a catalyst, which tends to produce unbranched chains with low octane ratings.

Prefix (IUPAC)

The part of the IUPAC nomenclature system that identifies various substituent groups in the molecule.

Parent (IUPAC)

The part of the IUPAC name that identifies the longest continuous carbon chain and tells how many carbon atoms are in that part.

Locant

The numbers used in a chemical name to give the positions of functional groups and substituents on the parent chain.

Suffix (IUPAC)

The part of chemical nomenclature that identifies the primary functional group of the molecule.

Homologous series

A series of compounds where each member differs from the next member by a constant unit, such as unbranched alkanes.

Dispersion forces

Intermolecular forces that increase with molecular surface area; they are the primary reason for increased boiling points in higher molecular weight alkanes.

Octan-1-ol Density Comparison

Alkanes and cycloalkanes have densities considerably less than $1.00\,g\,mL^{-1}$, the density of water at $4\,^\circ C$, causing them to float.

Bromine water test

A chemical test where alkanes show no reaction, leaving the orange-brown color of $Br_2$ in water unchanged.

Potassium permanganate test

A test using a purple solution of $KMnO_4$; alkanes do not react and thus do not decolorize this solution under normal conditions.

Chiral

A term describing an object or molecule that cannot be superposed on its mirror image.

Superposable

When one object can be placed on another so that all parts of each coincide; simple geometric objects like spheres are instances of this.

Constitutional isomers

Isomers that have the same molecular formula but different connectivity of their atoms.

Stereoisomers

Isomers that have their atoms connected in the same sequence but differ in the arrangement of their atoms in space.

Stereochemistry

The study of the spatial aspects of molecular structure.

Enantiomers

Stereoisomers whose molecules are nonsuperposable mirror images of each other.

Diastereomers

Stereoisomers whose molecules are not mirror images of each other.

Achiral

Molecules that are superposable on their mirror image and do not show optical activity.

Chirality center

A tetrahedral carbon atom that is bonded to four different groups.

Stereogenic center

Any atom at which an interchange of groups produces a stereoisomer.