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Organic Chemistry Chapter 1 Part 2 Notes

Professor Matthew Dematteo - University of Cincinnati
Course

Organic Chemistry I (CHEM2040)

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Students shared 23 documents in this course
Academic year: 2021/2022
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University of Cincinnati

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Organic Chemistry

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Chapter 1 Notes Part II Read Sec3ons 1 and 1 from your textbook and complete the following notes. Isomers What are isomers?

There are two classes of isomers we will discuss in our course. The first type that we will discuss for now are cons3tu3onal isomers. Define this term. (What do they have that are the same and how do they differ?) Constuonal isomers -

For now, we will focus on cons3tu3onal isomers. Draw the two different cons3tu3onal isomers for the molecular formula C 2 H 6 O.

Now try again by drawing two cons3tu3onal isomers for C 2 H 4 Cl 2.

One more 3me, draw three cons3tu3onal isomers with the formula C 3 H 8 O.

For molecular formulas containing rela3vely few atoms, drawing cons3tu3onal isomers can be preTy simple, but when they get more complicated, it is helpful to use an addi3onal tool: Degrees of Unsaturaon. What is a degree of unsaturaon?

A π bond (second bond of a double bond or second and third bonds of a triple bond) or a ring reduces the total number of hydrogens in the formula by 2, so they have the same effect on the molecular formula (reduce it from being “saturated” by the number of hydrogens it could hold). Determine how many degrees of unsatura3on are in each of the following molecules:

Calculang Degrees of Unsaturaon from a Molecular Formula If you are given a molecular formula of an unknown molecule (e., C 10 H 11 N 2 O 6 F) and asked to find the molecule’s degrees of unsatura*on follow these steps: 1. Use the number of carbons in the formula to determine the saturated formula using the formula CnH2n+

For the example formula above:

  1. Take the number of hydrogens in the saturated formula and subtract the actual number of hydrogens in the formula with the following modifica3ons: a. Add 1 H for every halogen in the formula b. Subract 1 H for every nitrogen in the formula This will tell you the number of H’s the unknown molecule is “missing”. (This will always be an even number - if you have an odd number, you have made an error.) For the example above:

  2. Now take this number of “missing” H’s by 2 to get the degrees of unsatura3on. (This will always be a whole number – if you have a frac3on, you have made a mistake). For the example above:

Prac3ce this by calcula3ng the number of degrees of unsatura3on in the formula C 7 H 8 NOBr.

N H

O

Determining Molecular Shape What are the two variables that define a molecule’s structure?

Bond Length What is the defini3on of bond length? Moving across a row (lef to right), as in the examples below, label the diagram to show the trend in bond length. C-H N-H O-H F-H Explain why this trend is this way. Moving down a group (top to boTom), as in the examples below, label the diagram to show the trend in bond length. H-F H-Cl H-Br H-I Explain why this trend is this way.

Bond Angle What does the bond angle determine? We need to determine how many groups are around a given atom. What is a group?

What theory is used to account for the shapes around given atoms and what does this theory state?

**In general chemistry you probably learned a larger set of shapes, we will only focus on a few in this course (because organic chemistry tends to involve only a subsec3on of the elements) In order to predict the shape of molecule what should you count? What should you ignore?

You need to know all of these shapes and bond angles for this course. You won’t be provided with a table of this informa3on because there are only a few that we will use repeatedly throughout the course

2 Groups Around an Atom

HCN How many atoms around the center atom (C)? How many lone pairs around the center atom (C)? What is the shape around C? What are the bond angles around C? 3 Groups Around an Atom BH 3 How many atoms around the center atom (B)? How many lone pairs around the center atom (B)? What is the shape around this central atom (B)? What are the bond angles around B?

H 2 CNH How many atoms around the N? How many lone pairs around the N? What is the shape around N (note the lone pair changes the name of the shape)? What are the bond angles around N? 4 Groups Around an Atom When drawing these molecules, we ofen use dashed lines and wedges to show perspec3ve. What is the meaning of each of the following: A normal solid line = A wedge = A dashed line (no3ce how the dashes are drawn) = CH 4 Redraw this with the perspec3ve conven3ons described above How many atoms around the C? How many lone pairs around the C? What is the shape around the C? What are the bond angles around the C?

NH 3 Redraw this with the perspec3ve conven3ons How many atoms around the N?

H C N :

B H H

H

:

C H H

N

H

C H

H H H

.. N

H

H H

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Organic Chemistry Chapter 1 Part 2 Notes

Course: Organic Chemistry I (CHEM2040)

23 Documents
Students shared 23 documents in this course

University: University of Cincinnati

Was this document helpful?
Chapter 1 Notes Part II
Read Sec3ons 1.4 and 1.7 from your textbook and complete the following notes.
Isomers
What are isomers?
There are two classes of isomers we will discuss in our course. The first type that we will discuss for now are
cons3tu3onal isomers. Define this term. (What do they have that are the same and how do they differ?)
Cons*tu*onal isomers -
For now, we will focus on cons3tu3onal isomers. Draw the two different cons3tu3onal isomers for the molecular
formula C2H6O.
Now try again by drawing two cons3tu3onal isomers for C2H4Cl2.
One more 3me, draw three cons3tu3onal isomers with the formula C3H8O.
For molecular formulas containing rela3vely few atoms, drawing cons3tu3onal isomers can be preTy simple, but when
they get more complicated, it is helpful to use an addi3onal tool: Degrees of Unsatura*on.
What is a degree of unsatura*on?
A π bond (second bond of a double bond or second and third bonds of a triple bond) or a ring reduces the total number
of hydrogens in the formula by 2, so they have the same effect on the molecular formula (reduce it from being
“saturated” by the number of hydrogens it could hold).
Determine how many degrees of unsatura3on are in each of the following molecules:

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