Condensed Structural Formulas

Summary

In this organic chemistry video, Brent Kadrowski explains condensed structural formulas, which are simplified representations of Lewis structures. He demonstrates how to draw these formulas for molecules like butane and ethanol, emphasizing the omission of bonds and lone pairs while retaining connectivity. Kadrowski also covers the representation of repeating groups and double bonds. The video further instructs on converting condensed formulas back to Lewis structures and discusses variations for representing carbon-oxygen double bonds, concluding with a mention of skeletal structures.

Takeaways

• 📚 Condensed structural formulas are simplified representations of Lewis structures that omit bonds and lone pairs, focusing on connectivity.
• 🔗 In condensed formulas, bonded atoms are grouped together, and repeated groups are denoted with parentheses and subscript numbers.
• ✏️ When drawing condensed formulas, remember that hydrogens are shown together but are not bonded to each other, and carbon typically forms four bonds.
• 🔄 Converting Lewis structures to condensed formulas involves grouping bonded atoms and omitting non-essential bonds, such as those in alkanes.
• 🔬 Double bonds in alkenes are represented by a pair of lines between carbon atoms in condensed formulas, emphasizing the connectivity.
• 🧪 Carbon-oxygen double bonds, like in ketones, are often abbreviated as 'CO' in condensed formulas, clarifying the bond without detailing lone pairs.
• 📝 Carboxylic acids and aldehydes have specific condensed formula representations to distinguish their functional groups from alcohols.
• 📐 The order of atoms in condensed formulas matters, especially for functional groups like aldehydes, where 'C-H-O' differs from 'C-O-H'.
• 🖌️ Aesthetic preferences may lead to variations in how double bonds are drawn, but the connectivity information remains consistent.
• 🔬 Understanding how to convert between Lewis structures and condensed formulas is crucial for accurately representing organic molecules in different contexts.

Q & A

What are condensed structural formulas in the context of organic chemistry?

Condensed structural formulas are abbreviated versions of Lewis structures. They leave out bonds and lone pairs but convey the same connectivity information, making them more compact and easier to draw.

Why are condensed structural formulas important for representing organic molecules?

Condensed structural formulas are important because they provide a more efficient way to represent organic molecules, especially when drawing them in text-based formats like word processing programs.

How are atoms that are bonded represented in condensed structural formulas?

In condensed structural formulas, atoms that are bonded are grouped together. For example, a carbon bonded to three hydrogens is represented as CH3, where 'C' is drawn, followed by 'H' and a subscript '3' to indicate three hydrogens.

Can you explain the representation of repeating groups in condensed structural formulas?

Repeating groups in condensed structural formulas are represented by enclosing them in parentheses and adding a subscript number to indicate the number of repeating units, such as (CH2)2 for two CH2 groups.

What is the significance of the order of atoms in condensed structural formulas?

The order of atoms in condensed structural formulas is significant as it represents the connectivity of the molecule. It should be read from left to right to maintain the correct structure of the molecule.

How do you represent a carbon-carbon double bond in a condensed structural formula?

A carbon-carbon double bond in a condensed structural formula is represented by drawing a pair of lines between the two carbon atoms, indicating the double bond.

What is the convention for representing a carbon-oxygen double bond in condensed structural formulas?

A carbon-oxygen double bond is typically represented simply as 'CO' in condensed structural formulas, without explicitly drawing the double bond line.

How do you differentiate between an aldehyde and an alcohol in condensed structural formulas?

In condensed structural formulas, an aldehyde is represented with the order C-H-O to indicate the carbonyl group, whereas an alcohol would be represented with C-O-H to show the hydroxyl group.

What is the purpose of the subscript numbers in condensed structural formulas?

Subscript numbers in condensed structural formulas are used to indicate the number of identical atoms or groups that are bonded to a central atom or to each other.

How can you convert a condensed structural formula back into a Lewis structure?

To convert a condensed structural formula back into a Lewis structure, you start with the central atom and add the groups and bonds as indicated by the formula, ensuring to follow the valency rules for each element.

Outlines

00:00

📚 Introduction to Condensed Structural Formulas

This paragraph introduces the concept of condensed structural formulas in organic chemistry. Brent Kadrowski explains that these formulas are a simplified way to represent molecules, omitting bonds and lone pairs while retaining connectivity information. The video is aimed at those with a basic understanding of Lewis structures. Two examples are given: butane and ethanol. In butane, the formula groups bonded to carbons are represented as 'CH3', 'CH2', and 'CH' with subscripts indicating the number of hydrogens. Ethanol is similarly simplified, with the hydroxyl group 'OH' not showing lone pairs. The paragraph emphasizes the importance of understanding the rules of bonding when interpreting these formulas.

05:00

🔍 Converting Lewis Structures to Condensed Formulas

The second paragraph delves into the process of converting Lewis structures to condensed structural formulas. It illustrates how to represent repeating groups with parentheses and subscripts, and how to handle different bonding scenarios, such as single and double bonds. Examples include variations of a molecule with three 'CH3' groups attached to a central carbon, and the representation of carbon-carbon double bonds. The paragraph also addresses the translation of carbon-oxygen double bonds, showing how to represent ketone and carboxylic acid structures in a condensed format. It concludes with the representation of aldehydes, emphasizing the correct order of atoms to distinguish them from alcohols.

Keywords

💡Condensed Structural Formulas

Condensed structural formulas are simplified representations of molecular structures that omit certain details like bonds and lone pairs to focus on connectivity. They are crucial for understanding the arrangement of atoms in organic molecules. In the video, Brent Kadrowski uses butane as an example to demonstrate how to convert a detailed Lewis structure into a more compact condensed form, emphasizing the ease of drawing these in text-based formats like Microsoft Word or Google Docs.

💡Lewis Structures

Lewis structures are a way to represent the valence electrons of atoms within a molecule, showing how they are shared between atoms to form chemical bonds. They are foundational to understanding condensed structural formulas, as they provide the detailed view that is then simplified. The video script mentions that a basic understanding of Lewis structures is necessary to grasp the concepts of condensed structural formulas.

💡Connectivity Information

Connectivity information refers to the way atoms are linked together in a molecule. Condensed structural formulas convey this information without showing every bond and lone pair, making them more concise. The video explains that even though details are omitted, the connectivity is preserved, which is vital for understanding molecular structure.

💡Bonded Groups

In the context of the video, bonded groups refer to atoms that are directly connected by covalent bonds. When drawing condensed structural formulas, these groups are represented together, such as 'CH3' for a carbon bonded to three hydrogens. This concept is used to illustrate how to simplify the representation of molecules like butane.

💡Subscript Numbers

Subscript numbers in condensed structural formulas indicate the quantity of a particular group or atom. For example, 'CH3' with a subscript '3' indicates three methyl groups. The video uses subscript numbers to show how to represent repeating units in a molecule, making the formula more compact and easier to read.

💡Carbon-Carbon Double Bonds

A carbon-carbon double bond involves two carbon atoms sharing four electrons, resulting in a strong bond. In condensed structural formulas, this is often represented by two lines between the carbon atoms. The video provides an example of an alkene to demonstrate how to represent such double bonds in a condensed form.

💡Carbon-Oxygen Double Bonds

Carbon-oxygen double bonds are common in functional groups like carbonyls. The video explains that these bonds are typically not drawn in condensed structural formulas, with the exception of aldehydes and ketones, where the double bond is implied by the presence of the functional group.

💡Functional Groups

Functional groups are specific groups of atoms within molecules that determine the chemical properties of the molecule. The video discusses how to represent various functional groups in condensed structural formulas, such as carboxylic acids and aldehydes, which are characterized by their unique bonding and reactivity.

💡Skeletal Structures

Skeletal structures are another way to represent organic molecules, focusing on the framework of the molecule without showing hydrogen atoms. The video mentions skeletal structures as an alternative to condensed structural formulas for representing molecules in a simplified manner.

💡Aesthetic Preference

Aesthetic preference in the video refers to the choice of how to draw certain parts of a molecule for clarity or ease of understanding. For example, the order of atoms in a double bond might be drawn differently to emphasize the nature of the bond, as seen in the representation of carbon-oxygen double bonds.

Highlights

Condensed structural formulas are abbreviated versions of Lewis structures that leave out bonds and lone pairs.

Condensed formulas convey the same connectivity information as Lewis structures but are more compact and easier to draw.

In condensed formulas, bonded atoms are grouped together, and groups are represented with subscripts to indicate the number of atoms.

The hydrogens in a group are shown together but are not bonded to each other, with each hydrogen making one bond.

Carbon typically makes four bonds, which is an important rule to keep in mind when interpreting condensed structural formulas.

Groups that repeat in a molecule can be represented by parentheses and a subscript number indicating the number of repeating units.

Ethanol is an example used to illustrate the conversion from Lewis structure to condensed structural formula.

In condensed formulas, lone pairs on oxygen are not represented, focusing only on the connectivity.

Multiple correct condensed structural formulas can be written for a given Lewis structure, showcasing flexibility in representation.

Condensed formulas can be converted back into Lewis structures by following a step-by-step process.

Double bonds in condensed formulas are represented by a pair of lines between carbon atoms.

The location of hydrogen and carbon can be swapped for clarity in representing double bonds, without changing the connectivity.

Carbon-oxygen double bonds are typically not drawn in condensed formulas, following chemical convention.

Carboxylic acids and aldehydes have specific representations in condensed formulas to distinguish their functional groups.

The order of atoms in the condensed formula for aldehydes is crucial to differentiate them from alcohols.

The video concludes with a suggestion to explore skeletal structures for another way to represent organic molecules.

The presenter, Brent Kadrowski, invites viewers to subscribe to his YouTube channel for more educational content.

Transcripts

hello everyone my name is brent

kadrowski and this organic chemistry

video is going to cover

understanding and drawing condensed

structural formulas

to understand this video you're going to

need a basic understanding of lewis

structures once you have that you should

be able to understand the condensed

structural formula concepts in this

video condensed structural formulas are

abbreviated versions of lewis structures

they leave out bonds and lone pairs and

they convey the same connectivity

information as lewis structures but

they're more compact and easier to draw

this is important if you're trying to

draw them

in a word processing program like

microsoft word or google docs

or some other text based format i have

two structures here that i'm going to

use to illustrate condensed structural

formulas

on the left is butane and in this

structure i've drawn in all of the bonds

as is typical for a lewis structure

in condensed structural formulas atoms

that are bonded are grouped together for

example

on the left side of the molecule there's

a carbon that's bonded to three

hydrogens

this group becomes ch3 where we draw out

the c

and the h and then we put a subscript

three behind it to indicate that there

are three of them

this is a bonded group now we're going

to move down the chain and take a look

at the next atoms attached

next there's a c with two h's attached

so we represent that as ch2 with the

subscripted two

moving down the chain there's another

carbon attached to two hydrogens which

is represented as

ch subscript two followed by a carbon

attached to three hydrogens which is

represented as ch subscript three this

is a condensed structural formula

for butane it doesn't contain any bonds

but it does convey connectivity

information

it's important to note that the h's are

shown together

but they're not bonded to each other

each hydrogen only makes one bond carbon

makes four bonds and it's important to

keep these rules in mind when you're

interpreting condensed structural

formulas

in condensed structural formulas groups

that repeat can be represented by

parentheses and a subscript number to

indicate the number of repeating units

for example in this molecule in the

middle there are two ch2 groups that

repeat

so this could be represented by

replacing the ch2ch2

with a ch2 and a parenthesis with a 2

around it to indicate the same thing it

just takes up less space

next we'll look at the example on the

right in a similar way we're going to

work from left to right to assign

the condensed structural formula in this

molecule of ethanol this is ethyl

alcohol so on the left there's a carbon

attached to three h's

we're going to call that a ch3 group so

c h

with a three subscripted then we'll move

on to the next part which is a carbon in

the middle with two hydrogens attached

that will be represented as ch2 with the

subscripted two

and finally there's the oh group and

notice here we're drawing oh but we're

not indicating the lone pairs on oxygen

they're important but they don't get

represented in the condensed structural

formula

here we're going to look at another

example of converting a lewis structure

to condensed structural formula

a lot of times there's more than one

correct condensed structural formula

that you can write for a given lewis

structure and that's certainly the case

with this example what i'm going to do

here is just show you a couple of ways

that you can represent it in a very

condensed form but there are other ways

that you could represent it as well

one strategy is to recognize that there

are three ch3 groups attached to a

central carbon and you can represent

those with a ch3

in parentheses with a subscript three

then you just finish the structure by

drawing ch to represent the central

carbon and hydrogen attached

another equivalent way to represent this

molecule would be to first write

hc to represent the central carbon and

its attached hydrogen

and then draw the three ch3 groups

afterwards both representations mean the

same thing and they're equally correct

this slide we're going to talk about how

to take a condensed structural formula

and convert it into a lewis structure

this is also a very important skill

here's an example of a condensed

structural formula that students have

had problems with in the past

we're going to go through this step by

step and describe how to convert this

into a lewis structure

so we'll start with the left side of the

molecule and read from left to right

the first thing to notice is that this

molecule starts with ch3ch2

parentheses three that means there's

three of these groups

attached to a central carbon atom we're

going to start with the central carbon

atom and draw that in first

then to that central carbon atom we're

going to draw the various groups that

are attached the three ch3 groups

then to that central carbon atom is also

attached a carbon with two h's we're

going to draw that next

following along with the structure that

carbon is attached to a carbon that's

attached to an h

and also a ch3 group that's indicated in

parentheses

moving along the chain there's another

ch

and that ch is attached to two ch3

groups

this slide talks about how to handle

double bonds and condensed structural

formulas

here's an example of an alkene this is a

molecule that contains a carbon-carbon

double bond

often times with carbon-carbon double

bonds people will draw in the cc double

bond as

a pair of lines between a couple of

carbons here's an example of how to

translate this lewis structure into a

condensed structural formula

we'll start on the left with the ch3

group

then follow up with the ch

then we'll draw a pair of lines and

another ch and that pair of lines

indicates the location of the

carbon-carbon double bond

we'll just finish up then with a ch2 ch3

you'll also potentially see this

molecule drawn as in the following

example

here it's just the location of the h and

the c that have been swapped the

connectivity information is the same

the reason people might do this is to

just emphasize that it's a carbon-carbon

double bond

for clarity mostly it's an aesthetic

preference

over on the right we have an example of

a carbon oxygen double bond

by convention most of the time the co

double bond isn't drawn

in although you may see it from time to

time here's an example of how to

translate this ketone structure into a

condensed structural formula

we'll start on the left with the ch2

group

and work our way to the right the c

double bond

o group is simply drawn as co in the

condensed structural formula

finally drawing ch3 completes the

molecule

when you're reading this condensed

structural formula it's important to

understand that the oxygen is doubly

bonded to the carbon highlighted in

purple

it isn't bonded in any way to the carbon

that's highlighted in red

sometimes people will clarify this by

drawing the oxygen in parentheses so

sometimes you'll see a variation of the

condensed structural formula drawn like

this

on the next slide we're going to go

through a couple more examples of

carbon-oxygen double bonds

we'll start off with a carboxylic acid

which has a c double bond

o attached to an o h group on the left

side of the molecule there's a ch3

and then on the right there's a carboxyl

group which contains the c double bond o

and the oh

this carboxyl group gets represented in

condensed structural formulas in a

couple of different ways

one option is to write c o to h

the other common option is to write

c-o-o-h

and you'll see these used

interchangeably they mean the same thing

the last example i'm going to go over is

an aldehyde an aldehyde has a formal

group which is c double bond

o h and this has to be represented in a

particular way in condensed structural

formulas to distinguish it from an

alcohol

as we've done before we'll start on the

left side of the molecule with ch3

then we'll move on to the formal group

represent this group by drawing

c-h-o it's important that the order be

c-h-o

and not c-o-h because o-h implies that

there's an alcohol functional group

which wouldn't be correct in this case

this concludes this video on condensed

structural formulas

check out my other video on skeletal

structures if you want to learn another

way to represent organic molecules in a

condensed format

if you found this video useful check out

the next one in the series or

watch the prior video and consider

subscribing to my youtube channel

my name is brent kadrowski thanks for

watching