Question

Draw the condensed structural formula for each of the following compounds: (a) 2-methyl-1-propene (b) 3,3-dimethyl-1-butyne

Short answer

(a) CH2=C(CH3)CH3; (b) CH≡C-C(CH3)2.

Step-by-step solution

Understanding the IUPAC Name

Identify the key parts of the IUPAC name to understand the structure of the compound. For (a) 2-methyl-1-propene: 'prop' indicates a three-carbon chain, 'ene' indicates a double bond, and '2-methyl' indicates a methyl group attached to the second carbon. For (b) 3,3-dimethyl-1-butyne: 'but' means a four-carbon chain, 'yne' indicates a triple bond, and '3,3-dimethyl' indicates two methyl groups attached to the third carbon.

Sketch the Carbon Backbone

Draw the backbone of the molecule. For 2-methyl-1-propene, draw a three-carbon straight chain. For 3,3-dimethyl-1-butyne, draw a four-carbon straight chain.

Add the Unsaturated Bond

For 2-methyl-1-propene, place a double bond between the first and second carbon atoms. For 3,3-dimethyl-1-butyne, place a triple bond between the first and second carbon atoms.

Add Methyl Groups

For 2-methyl-1-propene, add a methyl group to the second carbon. For 3,3-dimethyl-1-butyne, add two methyl groups both on the third carbon.

Write the Condensed Structural Formula

For 2-methyl-1-propene, the condensed structural formula is: CH2=C(CH3)CH3. For 3,3-dimethyl-1-butyne, the condensed structural formula is: CH≡C-C(CH3)2.

Key concepts

IUPAC Nomenclature

The IUPAC Nomenclature is a systematic approach to naming organic chemical compounds. This method allows chemists to communicate unambiguously about specific substances across the globe. The name of a compound under this system reflects its molecular structure. When you hear 'IUPAC name,' think of a code that reveals exactly how atoms are connected in a molecule.

Let's break down how this applies to 2-methyl-1-propene and 3,3-dimethyl-1-butyne:

• The first part describes the number of carbon atoms in the longest chain. 'Prop-' means three carbons, and 'but-' means four.
• Next is the nature of the unsaturation: 'ene' indicates a double bond, and 'yne' shows a triple bond.
• Finally, 'methyl' or 'dimethyl' indicates extra carbon atoms attached to that chain.
This descriptive naming helps visualize the structure just by reading the name, simplifying the process of drawing or recognizing the molecule in a lab or research.

Structural Formulas

Structural formulas are a graphical representation of how atoms are arranged and bonded in a chemical compound. In organic chemistry, these drawings give a clear view of carbon skeletons and the placement of different groups around them.

When it comes to compounds like 2-methyl-1-propene and 3,3-dimethyl-1-butyne, structural formulas allow chemists to specify exactly which type of bond (single, double, or triple) exists between atoms and where additional groups, like methyl groups, are positioned.

Here’s how to draw them:

• Begin with the carbon backbone, which is the longest chain of carbon atoms.
• Add unsaturated bonds (double or triple) between carbon atoms as described in the IUPAC name.
• Finally, include any additional groups, such as methyl groups, on the specified carbon atom.
• The end result should be a condensed structural formula, like CH₂=C(CH₃)CH₃ for 2-methyl-1-propene, neatly packing this structural information into a minimal number of symbols.

Condensed formulas are one type of structural formula, consolidating the structure to be quickly interpretable yet thorough, contributing to efficient communication in the chemistry realm.

Alkenes and Alkynes

Alkenes and alkynes are families of hydrocarbons known for their unsaturated nature, meaning they have double or triple bonds between carbon atoms. These bonds affect both the physical and chemical properties of the compounds, which is crucial when predicting reactions, like addition or polymerization reactions, they might undergo.

**Understanding Alkenes:** Alkenes, such as 2-methyl-1-propene, are characterized by at least one carbon-carbon double bond. This unsaturation allows them to participate in chemical reactions more readily than saturated hydrocarbons. For instance, the double bond gives rise to geometrical isomerism, a feature unique to compounds with restricted rotation around a bond.

**Exploring Alkynes:** Alkynes, like 3,3-dimethyl-1-butyne, have at least one carbon-carbon triple bond. These are even more reactive than alkenes because of the high energy contained in their triple bonds. They react in unique ways, such as undergoing hydrogenation to form alkanes or engaging in addition reactions that forge new chemical bonds.

Both alkenes and alkynes form the backbone of many important chemical reactions and have widespread applications in synthetic chemistry due to their reactivity.