Chapter 1 – Electronic Structure and Bonding: Part 1 of 3
Summary
TLDRIn this introductory organic chemistry lecture by Dr. Mike Chris Hansen, students are welcomed to the foundational concepts of the subject. The professor humorously sets expectations, emphasizing the course's goal to teach basic principles, organic synthesis, reaction predictions, and structure determination using IRMS and NMR data. He uses the analogy of Lego assembly to explain molecule synthesis and highlights the importance of organic chemistry in medicine, referencing the development of the drug Taxol. The lecture also reviews ionic and covalent bonds, electronegativity, and introduces Lewis, skeletal, and condensed structures, providing a solid groundwork for further study.
Takeaways
- 🎓 Dr. Mike Chris Hansen is a chemistry professor from Utah State University, introducing the organic chemistry course, Chem 2310.
- 🌟 Students can expect to gain a foundational understanding of organic chemistry, devise simple organic syntheses, predict chemical reaction outcomes, and determine compound structures using IR and NMR data.
- 📚 The course textbook is 'Organic Chemistry' sixth edition by Paula Yurkanis Bruice.
- 🤝 Organic chemistry is likened to assembling complex structures, like Legos, from simple pieces, but on a molecular level using chemical reactions.
- 🧪 The course covers the synthesis of complex molecules from commercially available starting materials, exemplified by the synthesis of the pharmaceutical drug Levan.
- 🌿 Most medicines are synthesized by organic chemists, including those originally derived from natural sources, due to the scarcity of naturally occurring quantities.
- 🔬 Organic chemistry's importance is highlighted by its role in pharmaceutical development, with organic chemists creating nearly every medicine used by humans.
- ⚖️ The lecture reviews the difference between ionic and covalent bonds, explaining how electron sharing differs between these types of bonds.
- 🔋 Electro negativity is introduced as a measure of an element's desire for electrons, influencing the polarity of bonds between atoms.
- 📝 Lewis structures are reviewed, detailing the steps for drawing them, which are essential for visualizing how atoms bond in molecules.
- 🔬 The lecture also touches on resonance structures and condensed structures, providing examples and their significance in organic chemistry.
Q & A
What is the main focus of Dr. Mike Chris Hansen's first lecture in the organic chemistry course?
-The main focus of the lecture is to introduce the basic principles of organic chemistry, the importance of the subject, and to set expectations for what students will learn throughout the course.
What is the humorous alternative that Dr. Mike Chris Hansen jokingly suggests students will gain from the course instead of the actual knowledge?
-Dr. Mike Chris Hansen humorously suggests that students will gain wealth, power, and prestige from the course, instead of the actual knowledge of organic chemistry.
What is the actual outcome students can expect to achieve from the organic chemistry course according to Dr. Mike Chris Hansen?
-Students can expect to understand the basic principles of organic chemistry, devise organic syntheses of simple molecules, predict the outcome of chemical reactions discussed in class, and determine compound structures using IR and NMR data.
What is the textbook that will be used for the organic chemistry course?
-The textbook used for the course is 'Organic Chemistry Sixth Edition' by Paully Yuranis Bruis.
How does Dr. Mike Chris Hansen compare organic chemistry to playing with Legos?
-Dr. Mike Chris Hansen compares organic chemistry to playing with Legos by explaining that just as complex Lego sets are assembled one piece at a time, organic chemists assemble complex molecules one step at a time from simple starting materials.
What is the significance of the yield percentage in a chemical reaction according to the lecture?
-The yield percentage is a measure of how efficient a chemical reaction is. The closer to 100%, the less material is wasted each time the reaction is run, indicating a more efficient process.
What is the role of organic chemists in the pharmaceutical industry as described in the lecture?
-Organic chemists are responsible for making or synthesizing molecules, often medicines, by using specific structure-altering chemical reactions to convert simple starting materials into complex products.
Why is it necessary to develop synthetic methods for medicinal compounds found in nature?
-It is necessary to develop synthetic methods because many medically useful molecules found in nature are present in such small amounts that it is not feasible to obtain enough of them to treat diseases without causing significant environmental harm.
What is the story of paclitaxel (Taxol) and how it relates to the role of organic chemistry in medicine?
-Paclitaxel, commonly known as Taxol, is a mitotic inhibitor used in cancer chemotherapy, originally isolated from the bark of the Pacific Yew tree. Due to the impracticality of obtaining it in large quantities from the tree, organic chemists, including Robert A. Holton, developed a synthetic method to produce it from 10-deacetylbaccatin III, a compound that can be harvested from the European Yew tree without killing it.
What is the concept of electronegativity and how does it relate to the formation of polar and nonpolar covalent bonds?
-Electronegativity is an element's ability to attract electrons in a bond. When there is a significant difference in electronegativity between two atoms, they form polar covalent bonds with a dipole moment. If the difference is minimal, they form nonpolar covalent bonds with even sharing of electrons.
How does Dr. Mike Chris Hansen describe the process of drawing Lewis structures in the lecture?
-Dr. Mike Chris Hansen summarizes the steps for drawing Lewis structures, which include counting valence electrons, placing atoms and single bonds, completing octets for all atoms except hydrogen, placing leftover electrons on the central atom, and using multiple bonds if necessary.
What are the differences between Lewis structures, skeletal structures, and condensed structures?
-Lewis structures show bonding electrons as dots and lone pairs. Skeletal structures simplify the Lewis structures by omitting some or all of the covalent bonds and listing atoms with subscripts. Condensed structures are a further simplification where the subscripts are also omitted and the atoms are simply listed in their connected order.
Outlines
📚 Introduction to Organic Chemistry Course
In this introductory lecture for the organic chemistry course, Dr. Mike Chris Hansen from Utah State University sets the stage for the semester, humorously suggesting that students will gain wealth, power, and prestige, before clarifying that they will actually learn the fundamental principles of organic chemistry. He outlines the course objectives, which include understanding organic chemistry basics, devising simple molecule syntheses, predicting chemical reactions, and determining compound structures using IR and NMR data. The text for the course is 'Organic Chemistry' by Pauly Yuranis Brus. Dr. Hansen also provides an analogy comparing organic chemistry to assembling Lego sets, emphasizing the step-by-step process of building complex molecules from simpler ones using specific chemical reactions.
💊 The Role of Organic Chemistry in Medicine
Dr. Hansen explains the significance of organic chemistry in the pharmaceutical industry, highlighting the role of organic chemists in synthesizing medicines from simple starting materials. He uses the example of the drug ESN proxin, derived from a complex synthesis process he was involved in during graduate school, to illustrate the efficiency of chemical reactions measured by percent yield. The lecture also touches on the importance of organic chemistry in creating medicines from natural products, such as paclitaxel (Taxol), which is synthesized from 10-deacetylbaccatin, a compound found in the European yew tree. This process allows for the large-scale production of life-saving drugs without depleting natural resources.
🔬 Understanding Bonding and Electronegativity
This section delves into the concepts of ionic and covalent bonds, explaining how electrons are shared or transferred between atoms. Dr. Hansen uses visual representations to illustrate electron density and partial charges in molecules. He introduces the concept of electronegativity as an element's tendency to attract electrons, noting that it increases across the periodic table. The lecture also covers the formation of polar and non-polar covalent bonds, influenced by the difference in electronegativity between bonded atoms, and the resulting dipole moments. Interactive questions are posed to engage students in identifying trends in electronegativity and understanding bond polarity.
📝 Lewis Structures and Molecular Representations
The final paragraph focuses on Lewis structures, summarizing the steps for drawing them and emphasizing their importance in understanding molecular geometry and bonding. Dr. Hansen provides a brief overview of the process, from counting valence electrons to completing octets and forming multiple bonds if necessary. He also introduces condensed structures, a simplified way of representing molecules by omitting non-essential bonds. The lecture concludes with a series of questions designed to test students' comprehension of Lewis structures, covalent structures, and condensed formulas, encouraging self-directed learning and problem-solving.
Mindmap
Keywords
💡Organic Chemistry
💡Chemical Bonding
💡Covalent Bond
💡Ionic Bond
💡Electronegativity
💡Polarity
💡Lewis Structures
💡Spectroscopy
💡Pharmaceuticals
💡Molecular Synthesis
💡Condensed Structures
Highlights
Introduction to the organic chemistry course by Dr. Mike Chris Hansen from Utah State University.
The course aims to teach the basic principles of organic chemistry, devise syntheses, predict chemical reactions, and determine compound structures using IRMS and NMR data.
The importance of organic chemistry in creating wealth, power, and prestige humorously introduced.
The text for the course is 'Organic Chemistry Sixth Edition' by Paully Yuranis Brus.
Organic chemistry likened to playing with Legos, where complex molecules are assembled from simple pieces.
The process of assembling molecules through specific chemical reactions, as illustrated by the synthesis of ESN proxin.
The significance of organic chemistry in the pharmaceutical industry for synthesizing medicines.
The role of organic chemists in developing scalable methods for producing medicinal compounds like Taxol.
The story of how organic chemistry made Taxol more accessible by synthesizing it from 10-deacetylbaccatin III.
The impact of organic chemistry on nearly all medicines, including those derived from nature.
The frustration expressed with medical professionals who may not fully understand the role of organic chemists.
Review of the difference between ionic and covalent bonds, and the concept of electron sharing.
Explanation of electro negativity and its influence on the polarity of covalent bonds.
The process of drawing Lewis structures, including steps and examples.
Introduction to the concepts of resonance structures and condensed structures in organic chemistry.
Interactive questions posed to the students to test their understanding of electronegativity and bond polarity.
The importance of understanding the electronic structure and bonding for the study of organic chemistry.
Upcoming lecture on electronic structure and bonding announced.
Transcripts
welcome my dear students to my first
video lecture for the semester one of
our two semester organic chemistry
course entitled chem
2310 I'm Dr Mike Chris chansen a
chemistry professor from Utah State
University and I'm excited to
indoctrinate I mean teach you about the
wonderful world of organic chemistry and
what should you hope to gain from this
course why wealth power and Prestige of
course I'm just kidding instead of all
that crap what you will learn if you
listen to and retain all the information
that I share over the course of this
entire lecture series is the following
one you'll learn to understand the basic
principles of organic chemistry two
you'll be able to devise organic
syntheses of simple
molecules three you'll be able to
predict the outcome of chemical
reactions discussed in class and four
you'll be able to determine compound
structures using irms and NMR
data now our text for this class or for
this YouTube lecture series for those of
you who aren't privileged enough to be
taking this from me in person will be
organic chemistry sixth edition by
paully yuranis bruis before we begin
however I'd like to First give you a
brief introduction to Organic Chemistry
by teaching you what it is and why it's
so
important organic chemistry is kind of
like playing with Legos trademark for
any of you who've played with Legos
trademark you might recognize that what
you see on the cover of the box is not
what you see when you open up the box so
how in the world do you convert all the
little pieces inside the box into the
actual playet featured well you do it
one piece at a time by following this
the instructions of course in this
particular example which I stole off the
internet you can assemble this Farmer's
watering hole for his dog and pig by
starting with this piece to which is
added these pieces to which are added
those pieces and so forth and so on
until we finally have the dog and the
Pig and the farmer next to watering hole
isn't that wonderful I thought you'd
like it organic chemistry then is very
similar just as we might assemble a
complex Lego play set one step at a time
by putting simple pieces together
organic chemists assemble complex
molecules one step at a time from simple
starting materials that can be bought at
a store unlike Legos however complex
molecules can't be assembled using our
hands they're just too tiny instead
they're put together by using very
specific chemical
reactions now just as an example I'd
like to show you guys the Assembly of a
molecule that I participated in
developing back when I was in grad
school starting with molecule one which
is cheap and commercially available from
several chemical supply companies uh the
research group I was in and I worked and
treated it under these conditions to
turn it into molecule 2 now you don't
have to understand at all what these
conditions are I just want you to
understand that they magically using
organic chemistry stuff that you don't
have to worry about right now turn
molecules like one into molecule two one
thing that I want to point out is that
this reaction was run in 98% yield what
does that mean well percent yield is a
measure of how efficient a particular
reaction is the closer to 100% a
reaction's yield is the less material is
wasted each time the reaction is run
thus we are again at chemists often try
to develop a lot of ways of increasing
our percent yields now with molecule 2
now in our hands on large scale we
reacted it under these conditions to
convert it into molecule 3 compound 3
was then converted to molecule four and
four was converted to five using a
special Catalyst that I haven't shown
here because honestly it structure is
really big and I don't think it'd fit on
this
slide finally at the very end molecule
five was converted into this molecule
shown right here which is known as ESN
proxin or more commonly it is
commercially known as the pharmaceutical
drug leave and just in case you're
interested in reading more here are two
publication references for the work that
we did on this project so once again
here's the point we organic chemists are
the people charged with the
responsibility of making or
synthesizing molecules which often are
medicines and we do so by using specific
structure altering chemical reactions to
convert simple starting materials into
complex products one step at a time now
many people don't realize that nearly
all the medicines that we buy and use as
human beings are made by organic
chemists and the processes by which they
are made are also invented by organic
chemists and chemical
Engineers but wait you might say don't
we get a lot of our medicines from
nature yes we do however most medically
useful molecules made by Nature are
found in such tiny amounts that we can't
get enough of them from nature to
actually treat disease hence natural
product chemists discover medicinally
useful molecules from nature and then
organic chemists develop ways of making
those molecules in large scale in the
lab I'll now illustrate this by telling
you a story that involves our molecule
of the
day paclet taxel which is commonly known
as taxol shown here is a mitotic
inhibitor used in cancer chemotherapy
that is isolated from the bark of the
Pacific U tree because it takes about
1.3 tons of ubar to get 10 g of taxon
and doing so kills the tree an
alternative means of developing large
amounts of taxol had to be developed I
hope you understand that natural
compound found out there but we'd have
to ravage nature in order to obtain
enough of it to actually treat any
disease so what do we do well in time a
compound called 10 detil bactin shown
here was found it happens to be made by
the European utree tendil Bon can be
harvested from the trees need needles
without uh killing the tree and they
grow back one thing you might notice if
you look at these two is that tends til
Bacon's core looks very very similar to
those of pacl taxel so in the late 1980s
and early 1990s Robert a Holton an
organic chemist from Florida State
University devised and patented a way of
synthesizing pacl taxel from tend detil
Bon using organic chemistry this
provided a scalable means of making
large amounts of this anti-cancer
medicine for clinical trials it's been
rumored incidentally that a good chunk
of Florida State's football team budget
is paid for by the royalties from this
patent uh though I don't actually know
if that's really
true so why do we care about organic
chemistry well the most significant
reason is that organic chemists use
organic chemistry to make nearly every
medicine in part or in whole that we use
as human beings even medicines that
originate from
nature thus pharmaceutic companies have
armies of organic Chemists in their
basement laborator slaving away like
Orcs to develop the treatments that we
use every day things like aspirin
oxycotton Viagra and liquid Joy note
liquid Joy is not a real product now I
have to mention that I sometimes find
myself feeling frustrated when I visit
with medical doctors or dentists who
don't seem to understand the role that
organic chemists play in their fields
now don't misunder understand me I'm not
trying to accuse all medical doctors and
dentists of such ignorance I did however
visit with one some number of years ago
who tried desperately to persuade me to
abandon my dream of becoming an organic
chemistry professor and to instead
pursue a career in the medical field
which no offense to doctors and dentists
just isn't my personal cup of tea to me
that was a little bit like a grocery
store owner trying to dissuade someone
from becoming a farmer frankly without
organic chemists medical doctors would
have to diagnose and treat dis
by shaking up bones in a
cup I know the
bones the Bones have
Fen so that takes us to our lecture
material for today I should warn you
that nearly all of the material in
today's lecture will review stuff that
you should have learned back in freshman
chemistry nevertheless it is pertinent
groundwork for understanding the rest of
organic chemistry so we will cover it
are you ready then good let's get
started after today's lecture you guys
should be able to do the following
distinguish between ionic and calent
bonds explain electro negativity
identify non-polar and polar calent
bonds and draw leis structures cacula
structures and condensed
structures first I'd like to start by
reviewing the difference between ionic
and calent bonds you see when two atoms
bond so that they they share each
other's electrons we say that they have
formed a calent bond when two atoms bond
so that one completely steals the
electrons from the other more or less we
call it an ionic
bond here's some pictures that show how
electrons spread across three different
molecules redder parts of those
molecules have more electron density
that is there's greater partial negative
charge there and Bluer Parts have less
electron density which means that
there's a greater partial positive
charge there our first example F2 shown
here which is also known as Florine gas
is formed when two individual Florine
atoms bond together when they do so they
share their electrons thus we can say
that they form a calent bond with even
sharing in our second example HF or
hydrofluoric acid the H and the F atoms
also share each other's electrons unlike
F2 however h and f do not share those
electrons even l so this is an example
of a calent bond in which there are
uneven sharing of
electrons in our third example l or
lithium fluoride the lithium atom has
more or less completely transferred its
single valence electron to the Florine
atom thus these two atoms are not
sharing electrons instead the Florine
has more or less completely stolen the
electron from the lithium this type of
bond is called an ionic bond because
there's a complete transfer of electrons
leaving two individual ions a lithium
positively charged cat ion and a
fluoride negatively charged
annion as mentioned when calent bonds
form sometimes the atoms in those bonds
share their electrons evenly and
sometimes they don't so what determines
the degree of
sharing electro
negativity and what is electro
negativity electro negativity simply
defin is an element's thirst for
electrons the more an element wants to
steal electrons to feel like a noble gas
I.E obtain a full octet the more Electro
negative that atom
is electro negativity increases as you
move up and to the right on the periodic
table noble gases the elements found in
column 8 of the periodic table are
excluded because they have very little
thirst of electrons because they already
have a full octet thus the most
electronegative element on the periodic
table is Florine and the least
electronegative atom is
francium this brings us to an impromptu
lecture question which atom in each of
the following pairs is the most
electronegative now I'm not going to
answer this question for you but we'll
instead let you Ponder and answer it for
yourself this is of course an excellent
exercise to determine if you can
identify Trends in electro
negativity
as I've already foreshadowed when two
bonded atoms have an electro negativity
difference the more Electro negative
atom will hog
electrons like this in this example
chlorine is much more electronegative
than hydrogen thus the chlorine pulls
electrons to itself much more strongly
than the hydrogen does kind of like a
tug-of-war between a monster truck and a
Volkswagen Beetle this uneven sharing of
electrons results in a partial positive
charge on the hydrogen and a partial
negative charge on the chlorine this
charge difference is called a
dipole the greater the difference in
electro negativity between two atoms the
more unevenly they share electrons and
the more polar their bond will
be we can often say then that bonds with
dipoles that is uneven sharing of
electron have dipole moments we can draw
a dipole moment in two different ways
one way is by drawing a partial positive
charge next to the atom that has a
partial positive charge and a partial
negative charge next to the atom that is
more electr negative another way is to
draw this this little arrow pointing
toward the more Electro negative atom
the one that is hogging the electrons to
itself more indicates that the electron
density is more heavily uh accumulated
on that atom coent bonds with dipoles
are called polar calent bonds and calent
bonds that do not not have dipoles are
called non-polar calent
bonds so this takes us back to our
original slide here as you can see when
two atoms have an even sharing of
electrons they have a non-polar calent
bond this happens when they have little
to no difference in electr negativity as
occurs in F2 when two atoms have a
more when two atoms have a more
significant difference in electro
negativity between them they evenly
share electrons this is called a polar
coent bond and lastly when two bonding
atoms have a really significant electro
negativity difference one atom will
completely transfer its electrons more
or less to the other and form an ionic
bond we might consider ionic bonds then
to be kind of like extremely polar coal
bonds this occurs most often when an
atom from the right side of the periodic
table bonds with an atom from the left
side of the periodic table because they
have such an extreme difference in
Electro negativities they will form an
extreme dipole in essence a complete
transfer of electrons from one atom to
the other giving an ionic
bond this brings us to another impromptu
leure question arrange each of the
following sets of bonds in order of
increasing
polarity and question two which of the
following bonds has a dipole for those
that have dipoles on which which atoms
do the partial positive and partial
negative charges lie once again I'm not
going to answer these questions for you
but we'll let you instead Ponder and
answer them for
yourselves we now move to a different
subject that of Lewis structures back in
general chemistry we learned how to draw
Lewis structures now I expect you to
know how to do this but I will not give
a thorough review here instead I will
just summarize the steps give you some
example problems to practice with if you
wish and provide some helpful links to
online tutorials on the subject if
needed please review section 1.4 of our
class text so here are the steps for
drawing L structures one add up all the
veence electrons for every atom in the
molecule if there are any anions in the
molecule add one electron to the total
number for each negative charge for cat
ions subtract one electron from the
total number for each positive charge
don't worry about which electrons came
from which atoms only only worry about
the total number two write the symbol
for all the atoms in the molecule
showing which atoms are attached to
which then connect them with a single
Bond or a dash which represents two
electrons chemical formulas are often
written in the order in which the atoms
are connected in many polyatomic ions
the first atom in the formula is the
central atom in the leou structure
usually but not always the central atom
is the less electronegative atom three
complete the octets around all the atoms
bonded to the central atom Except for
hydrogen which only wants two electrons
around it four Place leftover electrons
on the central atom even if doing so
results in more than an octet of
electrons around it and five if there
are not enough electrons to give the
central atom an octet try multiple bonds
such as double or triple bonds you got
that all right here are some more
electric questions on the subject
question one construct a leis structure
for O2 which each atom achieves an octet
of electrons two explain why it's
necessary to form a double bond in the
Le structure of
o2 and three draw loose structures for
each of the following
molecules and here's another question
the Le structure for the carbonate ion
is
what now once again I'm not going to
answer these questions but we'll instead
let you answer them for
yourselves we'll now finish this lecture
by briefly introducing you to two
different subjects Cula structures and
condensed structures in Cula structures
bonding electrons are drawn as lines and
lone pairs are usually left out unless
needed for some special reason here are
some
examples we often draw simplified
structures by omitting some or all of
the calent bonds and listing the atoms
with subscripts like this these types of
structures are called condens condensed
structures the condensed structures
shown here correspond to the Cula
structures that I showed in the previous
slide and now I finish by showing you
some more electric questions on this
subject question number two from our
problem set the culi structure of
pentane is shown here draw its condensed
structure
formula question three write a Le
structure for the following molecule ch2
Co and question four draw Cula
structures of the five different isomers
of C6
h14 well that brings us to the end of
this lecture please stay tuned for a
part two lecture on electronic structure
and bonding which will be posted shortly
until then have an enjoyable day
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