Structure & Stereochemistry of Alkanes (Ch. 3)

How are the longest chains drawn for organic compounds?

The longest chains are rarely drawn in a straight line; look carefully to find it.

What are the four rules that govern the IUPAC naming system? (Hint: NNOT!)

1. The Main Chain 2. Numbering the Main Chain 3. Naming Alkyl Groups 4. Organizing Multiple Groups

Define Degree of Alkyl Substitution

A degree determined by the number of carbons the main-chain carbon is bonded to. Prim

Define IUPAC Rules

A developed detailed system of nomenclature for organic compounds.

Define Alkane

A hydrocarbon that contains only single bonds. The general formula for this molecule is CnH2n+2

Define Alkenes

A hydrocarbon with a carbon-carbon double bond. The general formula of the hydrocarbon is CnH2n

Define Alkynes

A hydrocarbon with a carbon-carbon triple bond. The general formula of the hydrocarbon is CnH2n-2

Define Methylene Group

A methylene group is any part of a molecule that consists of two hydrogen atoms bound to a carbon atom.

Define Alkyl Group

A molecule with the general formula CnH2n+1. For example, Methane is CH4, but methyl is CH3.

Define Homologous Series

A series of compounds, like the unbranched alkanes, that differ only by the number of -CH₂- groups.

Why are alkanes hydrophobic?

Alkanes are nonpolar, so they dissolve in nonpolar or weakly polar organic solvents. They do not dissolve in water.

How reactive are alkanes?

Alkanes are the simplest and least reactive class of organic compounds because they contain only hydrogen and sp³ hybridized carbon, and they have no reactive functional groups.

What happens to alkanes in water?

Alkanes have densities around .7 g/mL, compared with a density of 1.0 g/mL for water. Because alkanes are less dense than water and insoluble in water, a mixture of an alkane (such as gasoline or oil) and water quickly separates into two phases, with alkane on top.

How do you name the alkyl groups?

Alkyl groups are named by replacing the -ane suffix of the alkane name with -yl.

What are homologs of propane?

Butane, Hexane, Decane, etc. Only differ in number of -CH₂-, no other group.

Define Common (Trivial) Names

Historical names arising form common usage.

Define Aromatics

Hydrocarbons with aromatic rings (resembling benzene). The ring with three carbon-carbon double bonds and three carbon-carbon single bonds.

When naming, if either end is closest to the first substituent, what must be done?

If each end had a substituent the same distance in, we would start at the end nearer the second branch point.

For what does the abbreviation IUPAC stand?

International Union of Pure and Applied Chemistry

What is the naming alkyl groups rule?

Name the substituent groups. Name the substituent groups attached to the longest chain as alkyl groups. Give location of each alkyl group by the number of the main-chain carbon atom to which it is attached.

What's an alternative term for IUPAC names?

Systematic Names

What is the process for naming complex substituents?

The base alkyl group is numbered beginning with the carbon atom (the head "carbon") bonded to the main chain. The substituents on the base alkyl group are listed with appropriate numbers, and parentheses are used to set off the name of the complex alkyl group.

What is the organizing multiple groups rule?

The final rule deals with naming compounds with more than one substituent. When two or substituents are present, list them in alphabetical order. When two or more of the same alkyl substituent are present, use the prefixes di-, tri-, tetra-, etc. to avoid having to name the alkyl group twice. Include a position number for each substituent, even if it means repeating a number more than once.

What is the main chain rule?

The first rule of nomenclature gives the base name of compound. Find the longest continuous chain of carbon atoms, and use the name of this chain as the base name of the compound.

Define Substituents

The groups attached to the main chain that replace (substitute) are hydrogen atom on the main chain.

How are the haloalkanes named?

The haloalkanes can be named just like alkanes, with the halogen atom treated as a substituent. Halogen substituents are named fluoro, chloro, bromo, and iodo.

Why are methane, ethane, propane, and butane named so?

The names, methane, ethane, propane, and butane have historical roots. From pentane on, alkanes are named using the Greek word for the number of carbons, plus the suffix -ane to identify the molecule as an alkane.

How acidic or basic are alkanes?

They are poor acids and bases, and they are poor electrophiles and nucleophiles as well.

What is the numbering the main chain rule?

To give the locations of the substituents, assign a number to each carbon on the main chain. Number the longest chain, beginning with the end of the chain nearest a substituent.

Define Homologs

Two compounds that differ only by one or more -CH₂- groups.

Define Hydrophobic

Water Hating; Water repelled.

Why do we start numbering from the end nearest a substituent?

We start the numbering form the end nearest a branch so the numbers of the substituted carbons will be as low as possible.

When naming, what must be done if there are two longest chains of equal length?

When there are two longest chains of equal length, use the chain with the greater number of substituents as the main chain.

What is the archaic term for pentyl?

amyl