20.1 Organic Chemistry -...

January 13 1 Organic Chemistry

20.1 Organic Chemistry

An Introduction to nomenclatures, structures and reactions

Dr. Fred Omega Garces Chemistry 201 Miramar College


Outline Organic Chem and the Carbon atom Atoms in Organic Compounds; Number of bonds

Representing Organic Compounds

Family Tree and Formula

Prefixes and suffixes

Degrees of Carbon Isomers

Alkyl Group

IUPAC nomenclature

Substituents

Alkenes and Alkynes ... geometric isomers

Aromatic compounds and nomenclature

Functional Group


What is Organic Chemistry ?

Organic Chemistry:

Study of carbon containing compounds.

Everything else is considered inorganic. Over 30 million chemicals from 120 known elements.

800 thousands are inorganic the rest are organic chemicals.

Why are there so many organic compounds?


The magic Carbon atom

Difference between organic and inorganic is C-atom ability to form very long chain

Inorganic compound will become unstable after with 12 or more atoms.

C-atoms ability to form very strong covalent bond means molecules can possess 100 or more atoms


Evolution of Organic Chemistry “Can man artificially create a living animal from chemicals ?”

- magnitude of question concerning organic compound

Prior to 1828, organic compounds can only be obtained from living organism

Fredrick Wohler prepared urea, a chemical in urine (an organic compound)

NH4Cl + AgNCO g NH2-CO-NH2 + AgCl

Now a days the bulk of organic compounds

is manufactured in the lab.

C

H2N NH2

O


Source of Organic Compound Organic chemicals isolate from nature. Nature

has her huge laboratory and is constantly synthesizing chemicals through biosynthesis.

Today we can manufacture these same chemicals in the lab

Mescaline

Caffeine Tetrahydrocannabinol THC

HO

H

H

HH

H

Ethanol


Lewis Dot Structure: Number of bonds for nonmetal atom

Lewis Dot Structure and VSEPR: revisited

H C N O X Val. e- 1 4 5 6 7

# Bonds 1 4 3 2 1 H-H CH4 NH3 H2O H-Cl


Forms of Carbons Carbons with single bond :

Methane, CH4 Tetrahedral 109.5° sp3

Carbons with double bonds ethene, C2H6 Trig. planar 120° sp2

Carbons with triple bonds

Ethyne C2H2 Linear 180° sp

HC CH


Structure - Ways of presenting organic Compounds

Consider: Ethanol and dimethylether C2H6O Molecular formula - indicate type and number of atoms

C2H6O C2H6O Structure formula - shows connectivity of atoms in a compound

Ethanol Dimethylether

Condense formula - shows connecting group of atoms in a compound Ethanol, CH3CH2OH Dimethylether, CH3OCH3

Shorthand notation - shows hydrocarbon as "R" and functional group as is. Ethanol R-OH Dimethylether R-O-R’

Stick (Skeleton) form - shows hydrocarbons as lines with functional group Ethanol Dimethylether

Isomers - Compounds that have the same formula but different structures Ethanol and dimethylether have the same formula but are different compounds

and therefore possesses different properties Ethanol is the drinkable alcohol, while dimethyl ether was used as an anesthetic.

OH O


Functional Group Name -Suffix group Example

1 Aliphatics -ane, -ene,-yen

, , , , propane, propene, proyne

2 Alcohol -ol =

propanol3 Ether - ether ,

ethylpropylether4 Aldehydes -al

, propanal

5 Ketones -one

, propanone

6 Carboxylicacid

-oic acid

, propanoic acid

7 Ester -ate,

methyl propanoate8 amine -amine

, triethyl amine

9 amide -amide

, N-methylpropamide

C C C C C C

OHOH

R O R ' O

R C OH C O

H

R CO

R 'CO

R CO

OH CO

OH

R CO

O R 'CO

O

R NR '

R ' N

NR '

R 'RC

ONHC

O


Organic Compounds; the Family Tree.

Organic Compounds

cyclo Aliphatics

Hydrocarbons Heteroatoms

Aromatic Aliphatics

Alkane

Alkene

Alkyne

O

CH 3 CH 3

C NH

O


Alkanes CnH2n+2

Hydrocarbons with only single bonds

Methane CH4

Ethane C2H6

Propane C3H8

Butane C4H10

Pentane C5H12

The Alkanes


Degree of Carbon

C

CH2

CH3

CH

CH3

CH3

CH3CH3


Degree of Carbon

a) primary carbons, 1° -

carbons bonded to only one other carbon

b) secondary carbons, 2° -

carbons bonded to two other carbons

c) tertiary carbons, 3° -

carbons bonded to three other carbons

d) quaternary carbons, 4° -

carbons bonded to four other carbons

C

CH2

CH3

CH

CH3

CH3

CH3CH3


Prefix and the Number of Carbons # of

CMolecularFormula

Prefix Alkanename

Structure and isomers

groupname

1 CH4 meth- methane CH4 methyl2 C2H6 eth- ethane ethyl3 C3H8 prop- propane propyl, i-propyl4 C4H10 but- butane

, butyl, iso-butyl

sec-butyl, tert-butyl5 C5H12 pent- pentane

, ,

pentyl

6 C6H14 hex- hexane etc... -

7 C7H16 hept- heptane -8 C8H18 oct- octane -9 C9H20 non- nonane -

10 C10H22 dec- decane -


Isomers are molecules with the same chemical formula but different structural formula.

Pentane (C5H12) n-pentane, iso-pentane, neo-pentane

Hexane (C6H14) n-hexane 2-methylpentane 3-methylpentane

2,3-dimethylbutane 2,2-dimethylbutane

Isomers


Alkyl group (in naming scheme) Alkyl group - An important idea in the naming scheme is the group of atoms

attached to a carbon chain. These have yl - suffix.

First 5 alkyl groups and their isomers:

1. Methyl 2. Ethyl 3. Propyl: n-propyl, isopropyl

4 .Butyl: n-butyl, sec-butyl, iso-butyl, tert-butyl

5. Pentyl: n-pentyl, sec-pentyl, iso-pentyl, neo-butyl

(Assignment, write the stick figures of these alkyl groups

H

HCH

H

H

HH

C

H

HC C

H

H H

HH

HC C

H

H

H H

H

methane g methyl ethane g ethyl

. .

H3C

C

CH3

CH H

H CH3

H2CCH2

H2C CH3

CH2

H2CH2C

CH3 CH2

H3C CHCH3

H3C

CH

CH3

CH2C

H3C CH3H3C


IUPAC Nomenclature Rules of the game: Alkane (CnH2n+2)

1. Find the longest continuous chain of carbon atoms. Assign this chain as the parent name . 2. Determine the substituents (groups) attached to the parent chain 3. Assign attachment position of group to main chain by starting at end closest to substituent group (or lowest number position).* 4. Identical groups attached to the main chain are designated with prefixes. 2-di, 3-tri, 4-tetra, 5-penta

5. Different groups attached to main chain are written in alphabetical order. 6. Alkyl halides: Halogen atoms (group) are designated as halogen prefix. F - Fluoro, Cl-Chloro, Br- Bromo, I- Iodo 7. Alkyl groups (see previous page)

•  The numbering scheme should be chosen such that the sum of the position in which group are attached add up to the lowest sum.

http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/nomen1.htm


•  Consider the following hexane compound: Heptane (C7H16)

1. Pentane

2. Methyl

3. Carbon # 2 & # 3

4. 2,3 = position methyl = group pentane = parent name

5. Two methyl, g dimethyl

6. Name: 2,3-dimethylpentane

IUPAC nomenclature, an example

2 3


• Alkyl • Methyl • Ethyl • Propyl: normal(n)-propyl, iso(i)-propyl • Butyl: normal(n)-butyl, iso(i)-butyl, sec(s)-butyl, tert(t)-butyl

• Halogens • Fluoro (F), Chloro (Cl), Bromo (Br), Iodo(I)

• Others • Nitro (NO2), Hydroxyl (OH), cyano (CN),

Common substituents


Alkenes CnH2n • Alkynes CnH2n-2 Hydrocarbons with multiple bonds

- Ethene, C2H4 - Ethyne,C2H2

- Propene, C3H6 - Propyne, C3H4

Note:

If there is more than one multiple bond g poly unsaturated i.e.,

Alkenes and Alkynes


More on Alkenes Geometric Isomers

Cis 2-butene Trans 2-butene Can’t rotate the double bond which makes these molecules unique compounds or specifically, Geometric isomers. Life example: 11-cis-retinal g all trans retinal

R

C

O

H

RH

Ohν

dark with enzyme Signals optic

nerve cell Visual pigment

(rhodopsin)


more rules of the game: Alkene (CnH2n) -ene (suffix)

1. - ene suffix for alkenes 2. Main chain must include the double bond, the number one carbon is the carbon closest to the double bond.

3. position of double bond indicated by prefix numbering location. 4. For multiple double bonds : di = 2 double bonds tri = 3 double bonds

Alkyne (CnH2n-2) -yne (suffix) 1. - yne suffix for alkynes 2. Nomenclature rules are similar to that of alkenes

Nomenclature: Alkenes and Alkyne

2-propyl-1-pentene

2-methyl-hepta -1,3,5-triene

3-ethyl-4-methyl-1-hexyne


1. Monosubstituted a. group benzene

nitrobenzene chlorobenzene bromobenzene ethylbenzene b. special names:

phenol toluene aniline benzaldehyde

2. Two substituted groups - use prefix for position

3. Three substituted groups - requires # scheme (lowest position scheme)

4. Benzene as a group - phenyl

Aromatics: nomenclature

NO2 Cl Br CH2CH3

OH CH3 NH2 CO

OH

Xo (ortho)

m(meta)p(para)

X1

2

34

5

X1

2

34

5


Functional Group Name -Suffix group Example

1 Aliphatics -ane, -ene,-yen

, , , , propane, propene, proyne

2 Alcohol -ol =

propanol3 Ether - ether ,

ethylpropylether4 Aldehydes -al

, propanal

5 Ketones -one

, propanone

6 Carboxylicacid

-oic acid

, propanoic acid

7 Ester -ate,

methyl propanoate8 amine -amine

, triethyl amine

9 amide -amide

, N-methylpropamide

C C C C C C

OHOH

R O R ' O

R C OH C O

H

R CO

R 'CO

R CO

OH CO

OH

R CO

O R 'CO

O

R NR '

R ' N

NR '

R 'RC

ONHC

O


What is the IUPAC names of the following alkanes: Draw the condensed structural formulas and the stick form for the following

i) 2,4-dimethyl-nonane ii) 3-methyl-4,4-diethyl-trans-2-heptene

iii) 1-ethyl-4-methyl-cyclohexane: Identify the functional group for each compound:

Organic: Examples

CO

CC

H3C

C

NH2

HO

HH

O

O

HO

C

ONH

H

CH3CO C CH3C

C

NH2HO

HH O

O

H O

CO

N HH

CH3

20.1 Organic Chemistry -...

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