3 Steps for Naming Alkanes | Organic Chemistry

Summary

In this educational video, Melissa Maribel, a personal tutor, outlines the essential steps for naming alkanes in organic chemistry. She emphasizes the importance of two tables: one for carbon chain prefixes and another for common substituents. The process involves identifying the longest chain, numbering it to prioritize lower substituent numbers, and recognizing substituent types. The video covers five cases, from single to multiple substituents, and highlights the need for alphabetical order in naming. It also encourages viewers to download the Organic Chemistry Survival Guide for further assistance.

Takeaways

• 📝 Alkane naming is crucial for organic chemistry exams and involves specific steps and rules.
• 🔢 Prefixes are used to denote the length of carbon chains, and every alkane name ends with 'ane'.
• 📐 The longest carbon chain is identified first, which is the basis for the alkane's name.
• 📍 Numbering the carbon chain should prioritize the lowest possible numbers for substituents.
• 🔄 When substituents are present, their positions are indicated by numbers, with no spaces in the name.
• 🌐 For structures with multiple substituents, list their positions in ascending order separated by commas.
• 📌 If substituents are the same, use prefixes like 'di-' for two, and always list them in alphabetical order.
• 🔑 Identifying the type of substituent (e.g., methyl, ethyl) is essential for accurate alkane naming.
• 🤝 Structures with different substituents require combining their names in alphabetical order with their positions.
• 🔄 In cases with multiple chains of the same length, prioritize numbering for the most substituents at the lowest numbers.
• 📚 Additional resources like the Organic Chemistry Survival Guide are available for further study and practice.

Q & A

What is the purpose of the prefixes in alkane naming?

The prefixes in alkane naming indicate the length of the carbon chain in the alkane molecule.

Who is the speaker in the video script?

The speaker is Melissa Maribel, who is introduced as a personal tutor.

What is the significance of the tables mentioned in the script?

The tables are extremely important for understanding the prefixes for carbon chain lengths and the common types of substituents in alkane naming.

How many main steps are there for naming alkanes according to the script?

There are three main steps for naming alkanes: finding the longest carbon chain, numbering the chain to have the most substituents and lowest numbers, and identifying the type of substituent.

What is the format for naming a structure with one substituent in alkanes?

The format is the number of the location of the substituent, followed by a dash, the name of the substituent, and the name of the longest carbon chain, without spaces and no capitalization.

In Case 1, why is the substituent numbered from left to right instead of right to left?

The substituent is numbered from left to right to always have the lowest number for the substituent, which is a rule in alkane naming.

What is the prefix for a five-carbon chain in alkanes?

The prefix for a five-carbon chain is 'pent-'.

How are substituents numbered when there are two or more of the same type in a structure?

When there are two or more of the same substituent, the numbers are separated by a comma, followed by a dash and the prefix for the number of substituents, and then the name of the substituent.

What is the rule for substituent naming when there are two different substituents in a structure?

When there are two different substituents, they should be written in alphabetical order, with their numbers indicating their location on the carbon chain.

In the case of structures with two different long carbon chains, what is the approach to naming them?

The longest carbon chain is identified first, then the chain is numbered to have the most substituents and lowest numbers, and finally, the substituents are identified and named in alphabetical order.

What is the significance of numbering the carbon chain to have the most substituents in CASE 5?

Numbering the carbon chain to have the most substituents allows for a more accurate and informative name, reflecting the complexity of the molecule.

What resource is mentioned in the script for further learning?

The Organic Chemistry Survival Guide and other resources are mentioned, with links provided in the description box.

What additional skill is encouraged to learn along with alkane naming?

The script encourages learning how to draw the structure when given the name, with a video provided for this purpose.

Outlines

00:00

📚 Alkane Nomenclature Basics

In this segment, Melissa Maribel introduces the fundamental principles of alkane nomenclature, emphasizing the importance of two key tables: one for carbon chain prefixes and another for common substituents. She outlines the three main steps for naming alkanes, which include identifying the longest carbon chain, numbering it to prioritize the lowest numbers for substituents, and identifying the type of substituent. This introduction lays the groundwork for understanding the specific cases of alkane naming that will be explored in the subsequent paragraphs.

05:04

🔍 Case 1: Naming Alkanes with a Single Substituent

Melissa demonstrates how to name an alkane with a single substituent, following the three-step process. She explains that the name format includes the location of the substituent, a dash, the substituent name, and the longest carbon chain name. The example given is a compound with a methyl group on a four-carbon chain, resulting in the name '2-methylbutane'. Melissa also notes that numbering can be done from either end of the chain, but the lowest substituent number is always preferred.

📝 Case 2: Alkanes with Multiple Identical Substituents

This paragraph delves into the naming of alkanes with two or more identical substituents. Melissa shows that the numbers of the substituent locations are separated by a comma and are prefixed by 'di-' to denote two of the same substituents. The example provided is a pentane with two methyl groups located at the 2nd and 3rd carbon atoms, leading to the name '2,3-dimethylpentane'. The correct numbering is chosen to achieve the lowest possible numbers for the substituents.

🌟 Case 3: Alkanes with Two Different Substituents

Melissa discusses the naming of alkanes with two different substituents, such as a methyl and an ethyl group. The substituents must be listed in alphabetical order, and their positions on the longest carbon chain are indicated numerically. The example alkane has a heptane as its base with substituents located at the 2nd and 3rd carbon atoms, resulting in the name '2-ethyl-3-methylheptane'. The process highlights the importance of choosing the numbering that gives the lowest numbers for each substituent.

🔄 Case 4: Alkanes with Different Length Carbon Chains

In this case, Melissa addresses the complexity of naming alkanes with two different length carbon chains. The example provided has a heptane as the longest chain with substituents at the 3rd and 4th carbon atoms. The substituents are a methyl and an ethyl group, which are listed in alphabetical order, leading to the name '3-methyl-4-ethylheptane'. This paragraph reinforces the principles of prioritizing the longest chain and lowest substituent numbers.

🔗 Case 5: Alkanes with Multiple Same Length Carbon Chains

The final case examines alkanes with multiple carbon chains of the same length, such as a nonane with a t-butyl group and two methyl groups. Melissa illustrates how to select the numbering that maximizes the number of substituents, resulting in the name '2,2,3-trimethylnonane'. This case study concludes the alkane naming tutorial, emphasizing the importance of understanding and applying the nomenclature rules correctly.

Keywords

💡Alkanes

Alkanes are a class of organic compounds characterized by their carbon atoms being connected by single bonds. They are saturated hydrocarbons, meaning they contain only carbon-carbon single bonds and are the simplest type of hydrocarbons. In the video, alkanes are the main focus, and the process of naming them is explained in detail, emphasizing the importance of understanding their structure for organic chemistry.

💡Prefixes

In the context of naming alkanes, prefixes are used to denote the number of carbon atoms in the longest continuous chain of the molecule. The prefixes range from 'meth-' for one carbon to 'non-' for nine, and so on, increasing by one for each additional carbon atom. The script explains the significance of these prefixes in identifying the longest carbon chain, which is a fundamental step in alkane nomenclature.

💡Substituents

Substituents are functional groups or atoms that replace hydrogen atoms in a hydrocarbon molecule. In the video, common types of substituents are highlighted, such as methyl and ethyl groups, which are essential for understanding how to name alkanes with branched chains. The script provides examples of how substituents are named and positioned in the alkane's name.

💡Carbon Chain

A carbon chain refers to the sequence of carbon atoms connected by covalent bonds in a molecule. In the script, the process of identifying the longest carbon chain is crucial for naming alkanes, as it determines the base name of the compound. The script illustrates how to find the longest chain and how it influences the naming process.

💡Numbering

Numbering in the context of alkane nomenclature involves assigning numbers to the carbon atoms in the chain to indicate the position of substituents. The video emphasizes the importance of numbering to achieve the lowest possible numbers for substituents, which simplifies the name and follows IUPAC nomenclature rules.

💡Methyl Group

A methyl group is a substituent consisting of one carbon atom bonded to three hydrogen atoms (CH3). In the video, the methyl group is used as an example of a common substituent in alkanes. The script explains how to name alkanes with methyl groups, such as '2-methylbutane,' indicating the position and type of the substituent.

💡Ethyl Group

An ethyl group is a two-carbon substituent with the formula C2H5. It is larger than a methyl group and is another common substituent in alkanes. The script discusses the importance of identifying ethyl groups and their position in the molecule, as well as the alphabetical order in which they are named alongside other substituents.

💡Di- Prefix

The prefix 'di-' is used in chemistry to indicate that there are two of a particular substituent in a molecule. In the script, 'di-' is used in the context of naming alkanes with two identical substituents, such as 'dimethylpentane,' where 'di-' signifies the presence of two methyl groups.

💡Alphabetical Order

When naming alkanes with multiple substituents, the IUPAC rules require that the substituents be listed in alphabetical order. The script mentions this rule when identifying and naming different substituents, such as placing 'ethyl' before 'methyl' in the compound name.

💡Organic Chemistry Survival Guide

The Organic Chemistry Survival Guide is a resource mentioned in the script that is presumably a study aid for students learning organic chemistry. It is suggested as a tool to help understand the content of the video, including the naming of alkanes and other organic chemistry concepts.

💡IUPAC Nomenclature

IUPAC stands for the International Union of Pure and Applied Chemistry, which sets the standard nomenclature rules for chemical compounds. The script refers to IUPAC nomenclature as the system used for naming alkanes, emphasizing the systematic approach to creating unique and descriptive names for each compound.

Highlights

Melissa Maribel introduces herself as a personal tutor for alkane naming.

Two essential tables for alkane naming are presented: prefixes for carbon chain lengths and common substituents.

The alkane naming process involves three main steps: finding the longest carbon chain, numbering for lowest substituent numbers, and identifying substituents.

Case 1 demonstrates naming with one substituent, emphasizing the format and numbering from the left for the lowest number.

Methyl group identification leads to the naming of 2-methylbutane in Case 1.

Case 2 explains naming alkanes with two of the same substituents, using commas and prefixes for numbering.

Dimethylpentane is the result of correctly numbering and identifying two methyl groups in Case 2.

Case 3 introduces the naming of alkanes with two different substituents, requiring alphabetical order.

Heptane with a methyl and ethyl group is named correctly by following the alphabetical rule in Case 3.

Case 4 addresses structures with two different long carbon chains, focusing on the longest and numbering for lowest substituent numbers.

The correct name for Case 4 involves a methyl at position 3 and an ethyl at position 4 on a heptane chain.

Case 5 discusses structures with multiple same-length carbon chains, emphasizing the importance of maximizing substituents.

In Case 5, the correct name for a nonane chain with three substituents is determined by choosing the numbering that maximizes substituents.

The Organic Chemistry Survival Guide and additional resources are mentioned for further learning.

A video on how to draw structures from given names is recommended for viewers to enhance their understanding.

Staying determined and believing in one's ability to learn alkane naming is encouraged.

Transcripts

Since we're naming alkanes we’ll go over 5 different cases you might see on your next exam.

Hello everyone, I’m Melissa Maribel your personal tutor,

and these two tables are extremely extremely important for you to know!

This first table shows the prefixes for the different lengths of carbon chains you may see.

Since we are naming alkanes every structure name will end with ane

This second table shows the most common types of substituents you will need to know.

For naming alkanes we will follow these 3 main steps each time.

STEP 1: Find the longest carbon chain

STEP 2: Number the carbon chain so we have the most substituents and lowest number at each substituent.

STEP 3: Identify the type of substituent

Let’s apply this to Case 1 Case 1: 1 substituent

For 1 substituent this is how we will format the name of the structure

Where the number is the location of the substituent, followed by a dash,

the name of the substituent and the name of the longest carbon chain.

There are no spaces and nothing is ever capitalized!

STEP 1: Find the longest carbon chain

There is 1, 2, 3, 4 so four carbons this way, or

1,2,3,4 carbons this other way, either way the longest carbon chain is 4.

The prefix for four is but- and it ends in ane for alkane so butane.

STEP 2: Number the carbon chain so we have the most substituents and lowest number at each substituent.

So if we numbered the carbon chain from left to right, the substituent would be at 2.

If we numbered it from right to left, the substituent would be at 3.

So we’ll keep it numbered from left to right since we always want the lowest number for our substituent.

We now know the location of the substituent is at 2.

STEP 3: Identify the type of substituent

There is only 1 C that is not already part of the main carbon chain so this is a methyl group. And we get 2-methylbutane

You know we could have numbered this differently by starting at

this end 1, 2, 3, 4 and it would have given us the same exact answer. Since the methyl is still at 2.

CASE 2: The structure has 2 of the same substituents

Here’s how we’ll format the name Whenever a structure has 2 or more

of the same substituent we separate the numbers with a comma, then there’s a dash,

a prefix goes in front of the name of the substituent followed by the longest carbon chain.

STEP 1: Find the longest carbon chain

We have 1, 2, 3, 4 ,5 this way, or 1,2,3,4,5 this other way.

We know that 5 is the longest carbon chain, the prefix for 5 is pent, so pentane.

STEP 2: Number the carbon chain so we have the most substituents and lowest number at each substituent.

Here are some different ways we could have numbered this structure.

This first one shows the substituents at 2 and 3 The second one shows the substituents at 3 and 4

And this third one also is at 3 and 4

The correct numbering is the first one since we get the lowest possible number for substituents.

So 2 comma 3 goes in front

STEP 3: Identify the types of substituents

We have two methyl groups

And since there are two of the same substituent the prefix for 2 is di, so

dimethyl and this is the name of our structure

CASE 3: The structure has 2 different substituents

Here’s how we’ll format the name

With the two different substituent names and the number, they are located at,

followed by the longest carbon chain.

STEP 1: Find the longest carbon chain

We have 1, 2, 3,4 5, 6,7 or 1, 2, 3,4 5, 6, 7

The Longest carbon chain has 7 Carbons, so heptane

STEP 2: Number the carbon chain so we have the most substituents and lowest number at each substituent.

Here are some other possible ways we can number this.

All the ways would give the same amount of substituents but only ways 1 and 2 have the lowest number at each substituent.

Way 1 and 2 will give you the same answer. I’ll pick way 1

STEP 3: Identify the types of substituents

We have a methyl and ethyl group. Note: Always write substituents in alphabetical order

So the ethyl goes first then the methyl and we’ll place the numbers where each substituent is at

and this is the correct name.

CASE 4: The structure has 2 different long carbon chains

Some structures have 2 completely different sized carbon chains, which we’ll see here.

STEP 1: Find the longest carbon chain

Let’s see what we have, 1,2,3,4,5

or 1,2,3,4,5,6 or 1,2,3,4,5,6

And 1,2,3,4,5,6,7 7 is the longest carbon chain, which is heptane

STEP 2: Number the carbon chain so we have the most substituents and lowest number at each substituent.

Here are 2 ways we could number the chains, this first way is the best.

Since substituents are at 3 and 4 rather than 4 and 5.

Because we always want the lowest numbers for each substituent.

STEP 3: Identify the types of substituents

We have a methyl group at 3 and an ethyl group at 4

And we always arrange our substituents in alphabetical order.

When we do that we get this.

CASE 5: The structure has multiple same length carbon chains

STEP 1: Find the longest carbon chain

1,2,3,4,5,6,7,8,9 or 1,2,3,4,5,6,7,8,9

9 carbons is nonane

STEP 2: Number the carbon chain so we have the most substituents and lowest number at each substituent.

Here are the different ways we can number the carbon chain.

Remember we want the way that gives us the most substituents

way 1 gives you only 1 substituent which is t-butyl which as you can tell it literally looks like a T.

But way 2 gives us 3 substituents, an ethyl group and two methyl groups located at the second carbon.

So this is the correct name

Don't forget to download your Organic Chemistry Survival Guide and

to check the resources that I have for you

in the description box all the links are going to be there.

And make sure you know

how to draw the structure when your given the name.

Don't worry that video's right here. And remember stay determined you can do this!