Naming Alkynes - IUPAC Nomenclature & Common Names

The Organic Chemistry Tutor
28 Apr 201813:15
EducationalLearning
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TLDRThis educational video script offers an in-depth guide on alkyne nomenclature, starting with common names like 'acetylene' and progressing to IUPAC rules. It illustrates the process of naming alkynes with various substituents, such as methyl and ethyl groups, and addresses complexities like multiple triple bonds and functional group priorities. The script also covers naming alkynes with benzene rings and provides examples to solidify understanding, concluding with a comprehensive look at alkyne naming in the presence of other functional groups.

Takeaways
  • 🔍 The common name for the simplest alkyne, C-H, is acetylene, which is also referred to as an alkyne due to the suffix 'yne'.
  • 📝 When naming alkynes with substituents, the common name is derived from the base alkyne and the substituents' names, such as 'methyl acetylene' for an alkyne with a methyl group.
  • 🔄 For alkynes with multiple substituents, the common name includes all substituents in alphabetical order, like 'dimethyl acetylene'.
  • 🧩 In IUPAC nomenclature, the numbering of the carbon chain is chosen to give the triple bond the lowest possible number, as in '1-butyne'.
  • 📚 The common name for an alkyne with an ethyl group attached is 'ethyl acetylene'.
  • 🔢 For IUPAC nomenclature, the position of substituents is indicated by numbers, and the triple bond is denoted by 'yne', as in '2-pentyne'.
  • 🔄 When substituents are on both sides of the triple bond, the common name lists them in alphabetical order, such as 'ethyl methyl acetylene'.
  • 🌐 If a benzene ring is attached to an alkyne, it is referred to as 'phenyl' in the name, resulting in 'phenyl acetylene'.
  • 🔄 In IUPAC nomenclature, numbering is done to give the first substituent the lowest possible number, as in '2-chloro-5-methyl-3-hexyne'.
  • 📐 When multiple functional groups are present, the one with the higher priority is given the lower number, such as 'hexene' for an alkene over an alkyne.
  • 🍷 If an alcohol functional group is present with an alkyne, the alcohol is given priority in numbering, as in '3-butyn-2-ol'.
Q & A

  • What is the common name for the simplest alkyne with a triple bond between two carbon atoms?

    -The common name for the simplest alkyne with a triple bond between two carbon atoms is acetylene.

  • How is the common name for an alkyne with a methyl group in front of the triple bond determined?

    -The common name for an alkyne with a methyl group in front of the triple bond is determined by adding 'methyl' before the base alkyne name, making it 'methyl acetylene'.

  • What is the systematic IUPAC name for an alkyne with a triple bond on the first carbon of a four-carbon chain?

    -The systematic IUPAC name for an alkyne with a triple bond on the first carbon of a four-carbon chain is '1-butyne'.

  • What is the common name for an alkyne with both a methyl group and an ethyl group attached to the triple bond?

    -The common name for an alkyne with both a methyl group and an ethyl group attached to the triple bond is 'ethyl methyl acetylene', with the groups listed in alphabetical order.

  • How do you name an alkyne with a benzene ring attached to the triple bond?

    -An alkyne with a benzene ring attached to the triple bond is named by replacing 'benzene' with 'phenyl' in the name, resulting in 'phenylacetylene'.

  • What is the IUPAC name for an alkyne with a triple bond on the third carbon of a six-carbon chain with methyl groups on the second and fifth carbons?

    -The IUPAC name for this alkyne is '2,5-dimethyl-3-hexyne'.

  • What is the common name for an alkyne with two phenyl groups attached to the triple bond?

    -The common name for an alkyne with two phenyl groups attached to the triple bond is 'diphenyl acetylene'.

  • When numbering an alkyne for IUPAC naming, which direction should you choose to give the triple bond the lowest possible number?

    -You should choose the direction that gives the triple bond the lowest possible number, which may be either left to right or right to left.

  • How do you determine the priority between an alkyne and an alkene functional group when naming a molecule?

    -The alkyne functional group has more priority than the alkene functional group, so the numbering should be done to give the alkyne the lower number.

  • What is the IUPAC name for an alkyne with a triple bond on the third carbon and a chlorine atom on the fifth carbon of a nine-carbon chain?

    -The IUPAC name for this alkyne is '5-chloro-3-heptyne'.

  • When an alkyne has both an alcohol and a triple bond, which functional group takes priority in IUPAC naming?

    -The alcohol functional group takes priority over the alkyne in IUPAC naming, so the numbering should be done to give the alcohol group the lower number.

Outlines
00:00
🧪 Basic Alkyne Nomenclature

This paragraph introduces the basics of alkyne naming, starting with common names like 'acetylene' for the simplest alkyne. It explains how to derive common names by identifying the alkyne portion and any substituents, such as methyl or ethyl groups, and then combining these to form names like 'methyl acetylene' or 'dimethyl acetylene'. The paragraph also touches on the IUPAC naming system, emphasizing the importance of assigning the lowest possible number to the triple bond and using the suffix '-yne' for alkynes.

05:03
📚 Advanced Alkyne Nomenclature with IUPAC

The second paragraph delves into more complex alkyne nomenclature using the IUPAC system. It discusses how to number the carbon chain to give the triple bond the lowest possible number and how to name substituents in alphabetical order, as seen in examples like '2-pen-tyne' and 'ethyl methyl acetylene'. The paragraph also addresses the naming of alkynes with multiple functional groups, such as when an alkyne is present with a benzene ring, which is referred to as 'phenyl acetylene' in common nomenclature.

10:05
🔍 Prioritizing Functional Groups in Alkyne Nomenclature

The final paragraph addresses the prioritization of functional groups in alkyne nomenclature. It explains that when an alkyne is present with other functional groups like alkenes or alcohols, the alkyne typically takes precedence, except in cases where the alcohol group has a higher priority. The paragraph provides examples of how to number the carbon chain to reflect this priority, resulting in names like '3-hexyne' for an alkyne with an alcohol group on carbon 2. It concludes with a summary of how to name alkynes using both common and IUPAC nomenclature, reinforcing the importance of understanding functional group priority.

Mindmap
Keywords
💡Alkynes
Alkynes are a class of hydrocarbons that contain at least one carbon-carbon triple bond. They are a key focus of the video, which aims to teach viewers how to name these compounds correctly. The script provides examples of alkynes, such as acetylene, and demonstrates the naming process, emphasizing the importance of the triple bond in determining the structure's name.
💡Common Names
Common names for chemical compounds are simpler, more colloquial terms used to describe them, often based on historical usage or ease of pronunciation. In the script, common names like 'methyl acetylene' and 'dimethyl acetylene' are used to describe alkynes, providing a more straightforward way to refer to these molecules before moving on to more systematic naming conventions.
💡IUPAC Nomenclature
The International Union of Pure and Applied Chemistry (IUPAC) has established a systematic method for naming chemical compounds. The video script uses IUPAC nomenclature to explain the proper way to name alkynes, emphasizing the need for a logical and standardized approach to ensure clarity and consistency in chemical communication.
💡Acetylene
Acetylene is a specific type of alkyne with the formula C2H2, which is the simplest alkyne. The script begins with acetylene, highlighting its common name and its significance as the base for naming more complex alkynes, such as when a methyl group is attached to form 'methyl acetylene'.
💡Methyl Group
A methyl group is a chemical group with the formula -CH3, consisting of one carbon atom bonded to three hydrogen atoms. The script uses the methyl group as an example of a substituent in alkynes, showing how its presence affects the naming of the compound, as in 'methyl acetylene' and 'dimethyl acetylene'.
💡Ethyl Group
The ethyl group, with the formula -CH2CH3, is another type of alkyl group that can be attached to alkynes. The script mentions ethyl as part of the naming process for alkynes, such as in 'ethyl acetylene', and demonstrates how to incorporate multiple substituents in the naming convention.
💡Substituent
In organic chemistry, a substituent is an atom or group of atoms that replace hydrogen atoms in a hydrocarbon. The script explains how substituents like methyl and ethyl groups are named and ordered alphabetically in the common names of alkynes, as seen in 'ethyl methyl acetylene'.
💡Phenyl Group
A phenyl group is a hydrocarbon group with the formula -C6H5, derived from benzene. The script discusses how to name alkynes that include a phenyl group as a substituent, using 'diphenyl acetylene' as an example, which demonstrates the application of aromatic chemistry in alkyne nomenclature.
💡Alkene
An alkene is a hydrocarbon with at least one carbon-carbon double bond. The script briefly touches on alkenes to compare their naming priority with alkynes, indicating that in cases where both functional groups are present, the alkene is given priority in the naming, as in '1-hexene'.
💡Alcohol Functional Group
An alcohol functional group contains a hydroxyl (-OH) group bonded to a carbon atom. The script explains that when an alcohol group is present alongside an alkyne, the alcohol takes priority in naming, as in '3-butyn-2-ol', reflecting the hierarchy of functional groups in organic nomenclature.
Highlights

Introduction to naming alkynes with a focus on common and IUPAC names.

Common name of the simplest alkyne, C-H, is acetylene, also known as ethyne.

Methyl acetylene is the common name for an alkyne with a methyl group attached to the acetylene.

Dimethyl acetylene is named when there are methyl groups on both sides of the triple bond.

IUPAC nomenclature involves numbering the carbon chain to give the triple bond the lowest possible number.

Ethyl acetylene is the common name for an alkyne with an ethyl group attached.

2-pentyne is the IUPAC name for an alkyne with the triple bond between the second and third carbons.

Ethyl methyl acetylene is the common name for an alkyne with both ethyl and methyl groups.

Phenyl acetylene is named when a benzene ring is attached to the carbon-carbon triple bond.

2,5-dimethyl-3-hexyne is an example of IUPAC nomenclature for an alkyne with multiple substituents.

Diisopropyl acetylene is the common name for an alkyne with isopropyl groups on both sides.

Diphenyl acetylene is named when two phenyl groups are attached to the triple bond.

Prioritizing substituents in IUPAC nomenclature: the lower number is given to the first substituent in alphabetical order.

When numbering from right to left, the triple bond should receive the lowest possible number in IUPAC naming.

Naming alkynes with multiple functional groups: the alkyne functional group takes priority over the alkene.

In the presence of both alkyne and alcohol functional groups, the alcohol group is given priority in naming.

Counting the longest carbon chain must include the alkyne functional group in IUPAC nomenclature.

3-propyl-1-heptyne is an example of naming an alkyne with a propyl group and a triple bond on the first carbon.

Transcripts

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AlkynesIUPACNomenclatureChemistryTutorialAcetyleneMethylEthylPhenylBenzeneOrganic Chemistry