organic chemistry - intro concepts lecture

7/31/2019 Organic Chemistry - Intro Concepts Lecture

1/23

Organic Chemistry - Introductory Concepts

I. Characteristics of Organic Compounds

A. Contain Carbon

B. Most Are Flammable

C. Have Low Melting Points

D. Have Low Boiling Points

E. Soluble in Nonpolar Liquids

F. Insoluble in Water (Polar Liquid)

G. Contain Covalent Bonds

H. Contain Many Atoms

I. Have Complex Structures

J. Do Not Conduct Electricity (Molten or In Soln)

II. Characteristics of Organic Reactions

A. Take Place Between Molecules

B. Are Slow

C. Gives Varied Products - Side Reactions

D. May Not Go Far Toward Completion - Low Yield

E. Involve Only A Portion Of The Molecule - Functional Group


2/23

III. Unique Features of Carbon

A. Forms Bonds with Self To Give Chains Or Rings

B. Form Multiple Bonds With Itself

C. Forms Strong Covalent Bonds (Single & Multiple) With OtherElements

D. Isomers Are Possible - More Than One Arrangement

IV. How To Draw Organic Compounds

A. Rules

1. Number of Bonds

Carbon - 4 bonds

S & O - 2 bonds

N & P - 3 bonds

H, Cl, Br, I - 1 bond

2. First Connect Carbons to Carbons

3. Make Certain That Every Carbon Has 4 Bonds

4. Consider Special Arrangements - Functional Groups

5. Begin To Fill In With Atoms

6. Make Certain That O, S, N, Etc. Have Correct Number ofBonds


3/23

B. Kinds of Formulas

1. Molecular

2. Structural Stick

3. Condensed Structural

4. Carbon Skeleton

C. Examples

1. C4 H 10

2. C5 H12


4/23

V. Functional Groups

A. Comments

1. All hydrocarbon chains with a given functional groupwill have a similar set of properties regardless of thenumber of carbons in the chain.

2. A hydrocarbon chain with a set number of carbons butcontaining different functional groups will demonstratedifferent properties.

3. Reactions occur at functional groups.

B. We will examine functional groups made up of

1. Carbons and Hydrogens

2. Oxygen& Sulfur

3. Nitrogen And Phosphorous

VI. Hydrocarbons - Contain Only C & H

A. Overview

1. Alkanes2. Alkenes3. Alkynes4. Cyclic Hydrocarbons5. Aromatic Compounds


5/23

B. General Formulas and Functional Groups

1. Alkanes

a. CnH (2n+2)

b. C-C

2. Alkenes

a. CnH (2n)

b. C = C

3. Alkynes

a. CnH (2n-2)

b. C = C

4. Cyclic Hydrocarbons

a. Cycloalkanes - Carbons are arranged in ring butonly C - C bondsare present

b. Bridgehead Cycloalkanes

c. Cycloalkenes - Carbons are arranged in Ring butonly C - C bonds except for one C = C bond

5. Aromatic Compounds- Deal With Later

6. Heterocylic Compounds - Deal With Later


6/23

VII. Isomerism

A. Definitions

1. Two or more carbon compounds can have the same kindsand numbers of atoms, but different arrangements ofatoms.

2. Each unique arrangementof atoms has its owncharacteristic propertiesand is called an isomer.

B. Concepts

1. There are different ways that two structures can differfrom one another, hence there are different kinds ofisomers.

2. To determine that two compounds are isomers you must:

a. Check to see that each structure contains thesame number of carbons, hydrogens, etc. as theother compoundand

b. Check to make certain that the two structural stickformulas are different from each other -nonsuperimpossible


7/23

C. Alkanes and Chain Isomerism - Differin the arrangement ofcarbons in the chain

1. Butanes

2. Pentanes

3. Hexanes


8/23

D. Alkenes & Alkynes and Positional Isomerism - Differ InLocationof C=C Or C = C In Chain

1. Butenes

2. Pentenes

3. Hexynes


9/23

E. Alkenes and Geometric Isomerism

1. Due To Lack Of Freedom Of Rotation Around C = CBond

2. Example - Two Isomers of 2-butene

3. Conditions Necessary For Geometric Isomerism

A. Must have a C=C double bond or ring

B. Two groups attached to each C of C=C must be different

4. Cis vs Trans

X X X

\ / \ /

C = C C = C

/ \ / \

X

cis trans


10/23

F. Chain - Ring Isomerism

1. Hexene vs Cyclohexane

CH2=CHCH2 CH2 CH2 CH3

2. Heptene Vs Methylcyclohexane

CH2=CHCH2 CH2 CH2 CH2CH3

CH3 -

G. Cycloalkanes and Geometric Isomerism

1. Two 1,2-dibromocyclohexanes

2. Two 1,3-dibromocyclohexanes


11/23

VIII. Aromatic Compounds

A. Definition and Characteristics -

1. Their Formulas They Appear To Be Very Unsaturated, but

They React As Though They Are Saturated Hydrocarbons -

2. We usually See Them As Six Membered Rings WithAlternating Double Bonds or Circle Inside Ring

a. Resonance Structures

b. Resonance Hybrid


12/23

B. Monosubstituted Derivatives of Benzene

C. Disubstituted Derivatives of Benzene

D. Polycyclic Aromatics

1. Fused Rings

2. Rings Not Fused


13/23

IX. Heterocyclic Ringed Compounds

A. Definition of Heteroatom - Non Carbon Atom That Appears InA Ring

B. Definition of Heterocyclic Compound - Ringed Compound WithNon Carbon Atom In The Ring

C. Ring Size

X. Nomenclature -

A. Common Vs IUPAC

B. First Ten Alkanes- Stem + Ending

CH4 - Methane

C2H6 - Ethane

C3H8 - Propane

C4H10 - Butane

C5H12 - Pentane

C6H14 - Hexane

C7H16 - Heptane

C8H18 - Octane

C9H20 - Nonane

C10H22 - Decane


14/23

C. Ending For Alkenes, Alkynes, Cycloalkanes, Aromatics

1. Alkenes - ene

number to locate the C=C

2. Alkynes -yne

number to locate the C = C

3. Cyclo (stem) ane

4. Cyclo (stem) ene


15/23

D. Branched Chains and Nomenclature

1. Find the longest continuous chain, and use thatnumber of carbons to determine the stem. Add theappropriate ending.

a. If alkene or alkyne requires that the double ortriple bond be located with a number How tonumber the chain

b. If alkane number the chain so any branches orsubstituents get the lowest set of numbers

c. Identify substituents

CH3 - methyl

CH3CH2- ethyl

Cl- chloro

Br - bromo

I- iodo

NO2- nitro

d. If more than one substituent, use prefixes

2 = di 6 = hexa

3 = tri 7 = hepta

4 = tetra 8 = octa

5 = penta 9 = nona

10 = deca

e. List the substituents alphabetically


17/23


18/23

XI. Reactions of Hydrocarbons

A. Alkanes

1. Relatively Inert

2. Combustion

CH4 + O2 (plenty) - CO2 + H2O

CH4 + O2 (limiting) C + H2O

3. Reaction with Cl2 or Br2 in Light

hR-H + Br2 -----> HBr + R-Br

R-H + Br2 -----> NR

B. Unsaturated Hydrocarbons

1. Meaning of Unsaturation

Has one or more C = C or C = C s

2. Combustion

C = C or C = C + O2 (plenty) C + H2O


19/23

3. Addition Reactions

a. Reaction with Br2

Test for Unsaturation


20/23

b. Addition of Hydrogen

4. Oxidation Reactions

a. Evidence of Oxidation

Increase in the number of O

Decrease in the number of Hs

Go from C O to C = O


21/23

b. [O] = Oxidizing agents

KMnO4

Cr2O7-2 / H+

CrO3

c. KMnO4 Rxn for Unsaturation

Alkane + KMnO4 ----->

Alkenes

Alkynes


22/23

d. Observations

Alkanes

Alkene

Alkynes

e. Baeyer's Test for Unsaturation

Add KmnO4 and observe

Saturated Remains purple

Unsaturated - Purple Brown

C. Aromatic Hydrocarbons

1. Combustion

C6H6 + O2 (plenty) C + H2O

Burns very sooty


23/23

2. Aromatic Substitution

Br2 + HBr + Br-

3. Oxidation with KMnO4

KMnO4 + NR

organic chemistry - intro concepts lecture

Documents