Condensed Structural Formulas
Summary
TLDRIn 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
- π Condensed structural formulas are simplified representations of Lewis structures that omit bonds and lone pairs, focusing on connectivity.
- π In condensed formulas, bonded atoms are grouped together, and repeated groups are denoted with parentheses and subscript numbers.
- βοΈ When drawing condensed formulas, remember that hydrogens are shown together but are not bonded to each other, and carbon typically forms four bonds.
- π Converting Lewis structures to condensed formulas involves grouping bonded atoms and omitting non-essential bonds, such as those in alkanes.
- π¬ Double bonds in alkenes are represented by a pair of lines between carbon atoms in condensed formulas, emphasizing the connectivity.
- π§ͺ Carbon-oxygen double bonds, like in ketones, are often abbreviated as 'CO' in condensed formulas, clarifying the bond without detailing lone pairs.
- π Carboxylic acids and aldehydes have specific condensed formula representations to distinguish their functional groups from alcohols.
- π The order of atoms in condensed formulas matters, especially for functional groups like aldehydes, where 'C-H-O' differs from 'C-O-H'.
- ποΈ Aesthetic preferences may lead to variations in how double bonds are drawn, but the connectivity information remains consistent.
- π¬ 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
π 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.
π 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.
Mindmap
Keywords
π‘Condensed Structural Formulas
π‘Lewis Structures
π‘Connectivity Information
π‘Bonded Groups
π‘Subscript Numbers
π‘Carbon-Carbon Double Bonds
π‘Carbon-Oxygen Double Bonds
π‘Functional Groups
π‘Skeletal Structures
π‘Aesthetic Preference
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
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