Naming Alkenes, IUPAC Nomenclature Practice, Substituent, E Z System, Cycloalkenes Organic Chemistry

Summary

This video script offers a comprehensive guide to alkene nomenclature, covering basic naming conventions, the distinction between cis and trans isomers, and the use of the Enz system for more complex molecules. It explains how to identify the longest carbon chain, assign numbers to double bonds for the lowest possible values, and determine the priority of substituents using atomic numbers. Examples are provided to illustrate the process of naming alkenes, including those with multiple double bonds and various substituents.

Takeaways

• 🔡 Alkene nomenclature begins with the common names of alkanes, followed by a suffix indicating the number of carbons and the presence of a double bond.
• 📏 The numbering of alkenes starts from the end nearest to the double bond to give it the lowest possible number.
• 🔄 The terms 'cis' and 'trans' describe the orientation of substituents around a double bond, with 'cis' being on the same side and 'trans' on opposite sides.
• 🔎 The IUPAC 'E'/'Z' system is used for more complex alkenes with multiple substituents, where 'E' indicates the highest priority groups are on opposite sides and 'Z' indicates they are on the same side.
• 🌐 The longest carbon chain containing the double bond is chosen for naming, and the double bond position is given the lowest possible number.
• 🏋️‍♂️ Priority of substituents is determined by atomic number, with larger atoms and groups having higher priority.
• 📚 Common alkane names are methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, and decane.
• 🔗 When two double bonds are present, the suffix 'diene' is used, and a comma separates the positions of the double bonds.
• 🔄 Cycloalkenes are named by adding '-ene' to the cycloalkane name, with the double bond assumed to be at carbon 1 unless otherwise stated.
• 📐 For alkenes with functional groups like halogens, the position and type of the functional group are indicated in the name.
• 🧪 The 'E'/'Z' notation is placed before the name of the alkene to specify the stereochemistry of each double bond.

Q & A

What is the common name for a four-carbon alkane?

The common name for a four-carbon alkane is butane.

How do you name an alkene with a double bond between carbons one and two?

An alkene with a double bond between carbons one and two is named as '1-butene'.

When naming alkenes, what is the preferred direction to count from to get the lowest numbers?

When naming alkenes, you should count from the direction that gives the lower numbers for the double bond.

What is the name of an alkene with a five-carbon chain and a double bond on carbon 2?

An alkene with a five-carbon chain and a double bond on carbon 2 is named '2-penene'.

How do you name an alkene with two double bonds?

An alkene with two double bonds is named with the suffix 'diene' and the positions of the double bonds are separated by a comma.

What is the name of a cycloalkene with a double bond?

A cycloalkene with a double bond is named by adding the suffix 'ene' to the name of the cycloalkane.

How do you name a cycloalkene with a double bond in a ring?

A cycloalkene with a double bond in a ring is named by adding the suffix 'ene' to the name of the cycloalkane, and the double bond is assumed to be on carbon 1 unless otherwise specified.

What is the difference between 'cis' and 'trans' isomers in alkenes?

In alkenes, 'cis' isomers have similar groups on the same side of the double bond, while 'trans' isomers have similar groups on opposite sides.

How do you determine the priority of substituents for the E/Z nomenclature?

The priority of substituents for the E/Z nomenclature is determined by atomic number, with higher atomic numbers having higher priority.

What is the name of an alkene with a double bond at carbon 1 and a methyl group on carbon 3?

An alkene with a double bond at carbon 1 and a methyl group on carbon 3 is named '3-methyl-1-cyclohexene'.

How do you name an alkene with multiple substituents attached to the double bond?

For alkenes with multiple substituents attached to the double bond, you use the E/Z system to determine the stereochemistry and then name the longest chain with the substituents in alphabetical order.