Question

How is the root name of an alkane modified to indicate that a given hydrocarbon contains a double or triple bond in its longest continuous chain?

Short answer

The root name of an alkane is modified to indicate the presence of a double or triple bond in its longest continuous chain by replacing the "-ane" suffix with "-ene" for a double bond or "-yne" for a triple bond. Additionally, the position of the bond is included in the name as a number. For example, "butene" for an alkene with four carbon atoms and a double bond, and "butyne" for an alkyne with four carbon atoms and a triple bond.

Step-by-step solution

Introduction to hydrocarbons

Hydrocarbons are organic compounds composed of hydrogen and carbon atoms. There are three primary types of hydrocarbons based on the types of bonds between the carbon atoms: alkanes (single bonds), alkenes (double bonds), and alkynes (triple bonds). The root name of a hydrocarbon depends on the number of carbon atoms present in the longest continuous chain.

Understanding the root names of alkanes

The prefix of an alkane depends on the number of carbon atoms in the longest continuous chain: 1. Meth: 1 carbon atom 2. Eth: 2 carbon atoms 3. Prop: 3 carbon atoms 4. But: 4 carbon atoms 5. Pent: 5 carbon atoms 6. Hex: 6 carbon atoms 7. Hept: 7 carbon atoms 8. Oct: 8 carbon atoms 9. Non: 9 carbon atoms 10. Dec: 10 carbon atoms The suffix "-ane" is added to indicate that all carbon-carbon bonds in the longest continuous chain are single bonds.

Modifying alkane root names for alkenes

Alkenes contain a carbon-carbon double bond. To indicate the presence of a double bond, the suffix "-ene" is added instead of "-ane". The numbering for double bond position starts from the end of the chain closer to the double bond. For example, if you have an alkene with four carbon atoms, you would use the root "but" and replace the "-ane" suffix with "-ene" to get "butene". If the double bond is between the first and second carbon atoms, it will be called "1-butene" or simply "but-1-ene".

Modifying alkane root names for alkynes

Alkynes contain a carbon-carbon triple bond. To indicate the presence of a triple bond, the suffix "-yne" is added instead of "-ane". Similar to alkenes, the numbering for the triple bond position starts from the end of the chain closer to the triple bond. For example, if you have an alkyne with four carbon atoms, you would use the root "but" and replace the "-ane" suffix with "-yne" to get "butyne". If the triple bond is between the first and second carbon atoms, it will be called "1-butyne" or simply "but-1-yne". In conclusion, to modify the root name of an alkane when a double or triple bond is present in the longest continuous chain, you replace the "-ane" suffix with "-ene" for a double bond or "-yne" for a triple bond. Additionally, you include the position of the bond in the name as a number.

Key concepts

Organic Chemistry

Organic chemistry is a branch of chemistry that studies the structure, properties, composition, reactions, and preparation of carbon-containing compounds. These include not only hydrocarbons, which are made up of only carbon and hydrogen, but also compounds with a variety of other elements. Carbon's unique property to form stable bonds with itself allows it to create a variety of complex structures, including chains and rings.

In organic chemistry, understanding the structure and bonding of carbon is crucial. The way carbon atoms are connected, and the type of bonds (single, double, or triple) they form, greatly influences the physical and chemical properties of the compound.

When naming organic compounds, especially hydrocarbons, there is a systematic method to help chemists easily identify and communicate specific molecules. This method, organized by the International Union of Pure and Applied Chemistry (IUPAC), is based on the number of carbon atoms in the longest continuous chain and the types of bonds present.

Alkanes, Alkenes, and Alkynes

Alkanes, alkenes, and alkynes are three main categories of hydrocarbons. The classification is based on the type of bond between carbon atoms.

**Alkanes** contain only single bonds. They are saturated hydrocarbons because they have the maximum number of hydrogen atoms bonded to carbon. Their names end with the suffix "-ane". Common examples include methane ( ext{CH}_4) and ethane ( ext{C}_2 ext{H}_6).

**Alkenes** contain at least one double bond between carbon atoms, making them unsaturated hydrocarbons. Their names end with the suffix "-ene". The simplest alkene is ethene ( ext{C}_2 ext{H}_4), commonly known as ethylene.

**Alkynes** feature at least one triple bond between carbon atoms, also classifying them as unsaturated. They are named with the suffix "-yne". A well-known alkyne is ethyne ( ext{C}_2 ext{H}_2), also known as acetylene.

Each of these hydrocarbons has unique properties and chemical behaviors, primarily determined by the type of carbon bonding.

Chemical Bonding in Hydrocarbons

Chemical bonding in hydrocarbons is central to understanding these compounds' structure and reactivity. In hydrocarbons, carbon atoms can form single, double, or triple bonds by sharing electrons with other carbon atoms or hydrogen atoms.

A **single bond** (sigma bond, or \( ext{C-C} \)) occurs when two electrons are shared between two carbon atoms. This type of bond is found in alkanes and allows for a relatively flexible structure. Single bonds are the longest and weakest type of covalent bond.

A **double bond** involves one sigma bond and one pi bond. The pi bond is above and below the plane of the atoms, resulting in stiffer structures than single bonds, such as in alkenes. Double bonds are shorter and stronger than single bonds, contributing to broader chemical reactivity.

**Triple bonds** include one sigma bond and two pi bonds, forming an even shorter and stronger bond as seen in alkynes. This makes alkynes very reactive. The additional pi bonds restrict the rotation around the bond's axis, giving these molecules a linear shape.

The bonding type affects not only the compound's name but also its shape, reactivity, and physical properties, which are crucial for various applications in chemistry and industry.