Organic Chemistry - How To Draw Lewis Structures
TLDRThis educational video script offers a comprehensive guide to drawing Lewis structures for organic chemistry, focusing on the bonding preferences of common elements. It explains the typical bonding patterns for hydrogen, carbon, nitrogen, oxygen, and halogens, and provides step-by-step examples for molecules like methane, methanol, ethylamine, ethyl chloride, dimethyl ether, acetaldehyde, ethene, acetylene, and hydrazine. The script also addresses how to adjust Lewis structures for charged molecules, emphasizing the importance of electron distribution and element valency.
Takeaways
- π¬ Hydrogen can only form one bond, which is a fundamental rule in drawing Lewis structures.
- π Elements like boron, carbon, nitrogen, oxygen, and fluorine can form multiple bonds, with boron typically forming three bonds in its neutral state.
- π Carbon prefers to form four bonds, nitrogen usually forms three, and oxygen typically forms two bonds in organic chemistry.
- π Halogens like fluorine, chlorine, bromine, and iodine generally form one bond and have seven valence electrons, needing one more to complete their octet.
- π Sulfur often forms two bonds but can also form six, depending on its need to achieve an octet.
- π§ Phosphorus and nitrogen both tend to form three bonds, while silicon and carbon both form four bonds.
- ποΈ The Lewis structure for methane (CH4) involves carbon forming four single bonds with hydrogen atoms.
- πΊ Methanol (CH3OH) has a carbon bonded to three hydrogens and an oxygen, which forms two bonds and has two lone pairs.
- π³ The Lewis structure for ethanamine (CH3CH2NH2) shows nitrogen forming three bonds and having one lone pair, while carbon forms four bonds.
- π¦ Ethyl chloride (C2H5Cl) involves a carbon bonded to a chlorine atom, which forms one bond and has three lone pairs.
- π Dimethyl ether has an oxygen in the middle forming two bonds with two methyl groups, each carbon in the methyl groups forms three bonds with hydrogens.
Q & A
What is the primary topic of the video?
-The video is about how to draw basic Lewis structures within the realm of organic chemistry.
How many bonds can hydrogen form according to the video?
-Hydrogen can only form one bond.
What is the typical number of bonds that carbon forms in its neutral state?
-In its neutral state, carbon likes to form four bonds.
How does the number of bonds formed by boron differ when it has a charge?
-When boron has a charge, it can deviate from its typical number of three bonds formed in its neutral state.
What is the Lewis structure for methane?
-The Lewis structure for methane consists of a carbon atom bonded to four hydrogen atoms, each with a single bond.
How is the Lewis structure for methanol different from methane?
-Methanol's Lewis structure includes a carbon atom bonded to three hydrogen atoms and one oxygen atom, which in turn is bonded to one hydrogen atom and has two lone pairs.
What is the general rule for elements that form three bonds?
-Elements that form three bonds, like nitrogen, typically have one lone pair.
Why can't the Lewis structure for CH3CHO be drawn with a single bond between the carbon and oxygen?
-A single bond would not satisfy the carbon's need for four bonds and the hydrogen's need for one bond, hence a double bond is required.
What is the functional group in C2H4 and what is its name?
-The functional group in C2H4 is a double bond between two carbon atoms, and it is known as an alkene.
How does the Lewis structure for ethyl chloride differ from that of ethene?
-In ethyl chloride, the chlorine atom forms a single bond with the carbon and has three lone pairs, whereas in ethene, there is a double bond between two carbon atoms.
How does the Lewis structure change for an oxygen atom when it gains or loses a hydrogen atom?
-When oxygen gains a hydrogen atom, it loses a lone pair and acquires a positive charge. When it loses a hydrogen atom, it gains a lone pair and acquires a negative charge.
Outlines
π§ͺ Basic Lewis Structures in Organic Chemistry
This paragraph introduces the fundamentals of drawing Lewis structures for organic chemistry, emphasizing the bonding preferences of common elements like hydrogen, carbon, nitrogen, oxygen, and halogens. Hydrogen forms one bond, while carbon and silicon aim for four, nitrogen and phosphorus for three, and oxygen for two. Halogens typically form one bond, needing one more electron to complete their octet. The paragraph illustrates the Lewis structures of methane and methanol, highlighting the step-by-step process of determining the correct arrangement of atoms and bonds.
π Drawing Lewis Structures for Various Organic Molecules
The second paragraph delves into the Lewis structures of more complex organic molecules, including ethylamine (CH3CH2NH2), ethyl chloride (CH3CH2Cl), and dimethyl ether. It explains the process of drawing Lewis structures by starting with the most electronegative atoms and ensuring that all atoms achieve their preferred number of valence electrons. The paragraph also covers the Lewis structures of acetaldehyde (CH3CHO), ethene (C2H4), and acetylene (C2H2), introducing the concepts of alkenes and alkynes with double and triple bonds, respectively. Additionally, it discusses the Lewis structure of hydrazine, a molecule with nitrogen atoms forming both single and triple bonds.
π Impact of Charges on Lewis Structures
The final paragraph addresses the impact of charges on the Lewis structures of molecules, specifically focusing on methanol and its anions and cations. It explains how the removal of a hydrogen atom from methanol results in a negatively charged oxygen with three lone pairs, while the addition of a hydrogen ion to methanol leads to a positively charged oxygen with one lone pair. The paragraph reinforces the idea that oxygen's bonding and lone pair count can vary depending on its charge state, providing a clear example of how to adjust Lewis structures to reflect ionic changes.
Mindmap
Keywords
π‘Lewis Structures
π‘Hydrogen
π‘Carbon
π‘Oxygen
π‘Nitrogen
π‘Halogens
π‘Sulfur
π‘Phosphorus
π‘Silicon
π‘Aldehyde
π‘Charges
Highlights
Introduction to drawing basic Lewis structures in organic chemistry.
Hydrogen can only form one bond.
Boron forms three bonds in its neutral state and can deviate when charged.
Carbon forms four bonds in its neutral state.
Nitrogen forms three bonds, oxygen two, and halogens one.
Halogens have seven valence electrons and need one more to complete their octet.
Sulfur can form two or six bonds depending on its valence electron configuration.
Phosphorus forms three bonds, and silicon forms four bonds like carbon.
Lewis structure of methane (CH4) is explained with carbon forming four bonds with hydrogen.
Lewis structure of methanol (CH3OH) is detailed, showing carbon, hydrogen, and oxygen bonding.
General trends for elements forming three bonds typically include one lone pair.
Oxygen forms two bonds and has two lone pairs when neutral.
Halogens form one bond and have three lone pairs.
Elements like carbon, nitrogen, oxygen, and fluorine aim for an octet of electrons.
Hydrogen, being in the first row, can only hold a maximum of two electrons.
Lewis structure of ethylamine (CH3CH2NH2) is explained with nitrogen forming three bonds.
Lewis structure of ethyl chloride (CH3CH2Cl) is detailed with chlorine forming one bond and having three lone pairs.
Lewis structure of dimethyl ether is explained with oxygen forming two bonds and having two lone pairs.
Lewis structure of acetaldehyde (CH3CHO) is detailed with a carbon-oxygen double bond.
Lewis structure of ethene (C2H4) is explained with a carbon-carbon double bond.
Lewis structure of acetylene (C2H2) is detailed with a carbon-carbon triple bond.
Lewis structure of hydrazine (N2H4) is explained with nitrogen forming three bonds and having one lone pair.
Impact of charges on Lewis structures, such as CH3O-, CH3OH, and CH3OH+, is discussed.
Oxygen's bonding changes with charge: one bond with a positive charge, three bonds with a negative charge.
Transcripts
in this video we're going to talk about
how to draw some basic lewis structures
within the realm of organic chemistry
so let's go over some basic things you
need to know
hydrogen can only form one bond
elements like boron carbon nitrogen
oxygen fluorine they could form multiple
bonds
boron likes to form three bonds
when it's in its neutral state
now when it has a charge it can deviate
from this number
carbon and its neutral state likes to
form four bonds
nitrogen likes to form two i mean three
oxygen likes to form two and a halogens
like to form one
so like fluorine chlorine bromine iodine
those elements they like to form one
bond they have seven valence electrons
and they only need one more to get to
eight
sulfur likes to form two bonds but
sometimes it could form six
it has six valence electrons it can
either
try to acquire two to get to eight so in
that case it's going to form two bonds
or it can give away its six valence
electrons and form six bonds in the case
of sulfate
phosphorus like nitrogen likes to form
three bonds
silicon like carbon likes to form four
bonds
but these are the most common elements
that you're going to be dealing with
in organic chemistry
so let's say if we want to draw the
lewis structure
for methane
you know that carbon likes to form four
bonds and hydrogen can only form one
bond
so the only way to put this together is
to do it like this
and so that is the lewis structure of
methane
what about this example
methanol
ch3oh a type of alcohol
how can we draw the lewis structure for
that molecule
so let's view the molecule from left to
right so we have a carbon
and that carbon has three hydrogens
attached to it
and each hydrogen can only form one bond
now the carbon is attached to an oxygen
and oxygen likes to form two bonds
so this is the typical structure of
oxygen
it likes to form two bonds and has two
lone pairs
and then we have a hydrogen
and so this is the lewis structure for
methanol
so make sure you know this hydrogen
likes to form one bond carbon
likes to form four bonds
nitrogen
likes to form three bonds
and for elements that form three bonds
typically they have one lone pair
these are the general trends there's
always some exceptions so keep that in
mind
now oxygen
which likes to form two bonds has two
lone pairs
and the halogens like fluorine and
chlorine and things like that
they like to form one bond but they're
going to have three lone pairs
elements like carbon nitrogen oxygen
fluorine they like to have eight
electrons around them
hydrogen is in the first row so it can
only hold a maximum of two electrons and
that's why it can only form one bond
let's try another example
ch3ch2
nh2
so go ahead and draw the lewis structure
for that molecule
so viewing it from left to right we're
going to start with the ch3 so we have a
carbon attached to three hydrogen atoms
and then we have a ch2
so that's a carbon that's attached to
two hydrogen atoms
and attached to that is an nh2
now nitrogen likes to form three bonds
and hydrogen can only form one
so this nitrogenous rebonds and
typically it has one lone pair with
those three bonds
so this is the structure of ethoamy
now go ahead and try this one
ethyl chloride
feel free to pause the video
so we're going to follow the same
pattern we have a ch3
attached to a ch2
and then that's attached to a chlorine
atom
now chlorine is a halogen and typically
they form one bond and they're going to
have two lone i mean three lone pairs
rather than two
and so this is the lewis structure for
ethyl chloride
now let's work on another example
dimethyl ether
go ahead and draw the lewis structure
for that
so i'm going to start with the oxygen in
the middle
oxygen likes to form two bonds and on
each side we have a methyl group or ch3
group
and we know each of those carbons
contain three hydrogens
an oxygen when it has two bonds it's
going to have two lone pairs
and so that's the lewis structure for
dimethyl ether
now what about this one ch3cho
how can we draw the lewis structure for
this molecule
so the left side ch3 at this point we're
pretty familiar with it it's just a
carbon with three hydrogens
now this carbon needs four bonds so
we're going to draw another bond
and the next thing that it's attached to
is a carbon atom
now how can we draw c h o
well we can't draw like this because
hydrogen will have two bonds and that's
not going to work and we can't draw this
way because
carbon won't have four bonds
the only way in which we can make carbon
to have four bonds and hydrogen to have
one and oxygen to have two
is to put a double bond between the
carbon and the oxygen and connect the
carbon directly to the hydrogen
as you can see every element has their
desired number of bonds
and so this is the lewis structure for
ch3cho
this is a type of aldehyde specifically
acetaldehyde
this is how you spell the name
aldehydes typically have this functional
group that you see here
next up is c2h4 go ahead and try that
draw the lewis structure for that
molecule
so how should we begin are the two
carbons connected to each other or
how do we even draw this thing
when you see something like this
draw the carbon atoms first
now there's four hydrogens
the best thing to do is to split the
number of hydrogens equally among the
two carbons
you don't want to put three hydrogens on
one carbon
and one hydrogen on the other
because the carbons are the same so
they're going to have the same
attraction to those hydrogen atoms
the best thing to do
is to draw the molecule of symmetry
so begin by putting two hydrogen atoms
on each carbon
now you know that carbon wants to have
four bonds and right now each carbon
atom has two
so the only way to make each carbon
atoms have four bonds is to put a double
bond in the middle
and so that is the structure of c2h4
also known as ethene
it's a type of alkene
so anytime you see
a double bond between two carbon atoms
the functional group is an alkene
now let's move on to our next example
and that is
c2h2
go ahead and try that one
so let's start with two carbon atoms
and we're going to put a hydrogen on
each one
now the only way for each carbon atom to
have four bonds is to put a triple bond
in the middle
and so this molecule is known as
acetylene
and a functional group
is an
alkyne which corresponds to a triple
bond between two carbon atoms
now what about this molecule hydrazine
how can we draw the lewis structure for
it
now this is going to be very similar to
c2h4
so we're going to put the two nitrogen
atoms in the middle
and we're going to start by placing two
hydrogen atoms
on each nitrogen atom now we know that
nitrogen likes to form three bonds so
right now each of them have two which
means that we need a single bond between
the two nitrogen atoms now nitrogen
likes to have one lone pair
so we can
draw it that way
so that's the structure of hydrazine
now let's talk about what to do when you
have charges
so i want you to draw these three
molecules ch3o minus
ch3oh
and ch3oh
plus
so let's start with a familiar example
one that we covered already methanol
you know what i'm not going to draw the
ch3 part
i'm just going to leave it like this ch3
now the oh part is what i'm going to
focus on
so we know that oxygen likes to form two
bonds
and so it's going to have two lone pairs
but what's going to happen if we take
off the hydrogen on the oxygen
the two electrons in this bond they're
going to be pulled back to the oxygen
oxygen is more electronegative than
hydrogen and so it has a partial
negative charge
and so when this bond breaks those
electrons will be returned to the more
electronegative elements can be pulled
by it and so this oxygen is going to
have three lone pairs
as opposed to two and now it has a
negative charge
now what about if the oxygen gains a
hydrogen what's gonna happen
what we're gonna do is react methanol
with a hydrogen ion
now we said that oxygen has a partial
negative charge and so it's attracted
to the positively charged hydrogen ion
and so it's going to use a lone pair to
form a bond between the oxygen and the
incoming hydrogen
and so we're going to get a structure
that looks like this
i'm running out of space here
so this lone pair is gone
and those electrons are now in this bond
and so this oxygen has one lone pair
left but now it bears the positive
charge
and so whenever you have an oxygen with
a positive charge
note that it loses a lone pair to form a
new bond and when it has a negative
charge
it gained a lone pair to break a bond
so as you can see whenever you have
charges
oxygen won't have two bonds when it has
a negative charge it typically has one
bond
when it has a positive charge it
typically has three bonds but when it's
neutral
it has its standard number of two bonds
so those are some things you want to
keep in mind but that's it for this
video that's all i got thanks for
watching
you
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