Organic Chemistry

Guided by Ms. J.S. Pote

An organic compound is one that has carbon as the principal element •Carbon is unique •It has 6 electrons in its outer shell arranges 1s22s2sp2

e

e

e

e

•It has room for 4 bonds to 4 other atoms. e e

Organic compounds have specific geometry around the carbon to carbon bond

The carbon atom forms bonds in a tetrahedral structure with a bond angle of 109.5O.

So a chain of carbon atoms makes a zigzag pattern

•Introduction •A hydrocarbon is a compound consisting of only hydrogen and carbon. •The carbon to carbon can be single, double, or triple bonds. •The bonds are always nonpolar

Carbon-to-carbon bonds can be: Single

Triple. Double

Note that in each example, each carbon atom has four dashes, which represent four bonding pairs of electrons, satisfying the octet rule.

Carbon-to-carbon chains can be (A) straight

(B) branched

(C) closed ring.

Naming alkanes

•Identify the longest continuous chain. •The locations or other groups of atoms attached to the longest chain are identified and numbered by counting from the end of the molecule which keeps the numbering system as low as possible. •Hydrocarbon groups that are attached to the longest continuous chain and named using the parent name and changing the –ane suffix to –yl

Step-1 Identify the longest continuous chain • Where is the longest continuous chain of carbons?

Prefixes for root word of Carbons n 1

Meth

6

Hex

2

Eth

7

Hept

3

Prop

8

Oct

4

But

9

Non

5

Pent

10 Dec

Endings • Alkanes (all C-C single bonded parent chain) end in –ane – Methane CH4 – Ethane C2H6 – Propane C3H8

• Attached carbon groups (substituents) end in –yl – Methyl CH3 – Ethyl CH3CH2– Propyl CH3CH2CH2 –

3-ethylpentane

Step 2. Number the parent chain. • Number the parent chain so that the attached groups are on the lowest numbers Methyl is on carbon #2 of the parent chain Methyl is on carbon #4 of the parent chain 1 5

18

2 4

27

3 3

4 2

5 1

red is the right way for this one!

Groups on 4, 6, and 7

36

72

45

54

81

63

Groups on 2, 3, and 5

1 1

2 6

3 5

4 4

5 3

6

72 1 Groups on 2 and 5 Groups on 3 and 6

Step 3. Name the attached groups. • Carbon (alkyl) groups – Methyl CH3 – Ethyl CH3CH2– Propyl CH3CH2CH2 –

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

Step 4. Designate where the group is attached to the parent chain. • Use the numbers of the parent chain from step 2 to designate the location of the attached groups to the parent chain. 2-methyl

1

2

3

4

5

Step 5. Alphabetize the groups, combine like groups, and assemble. • The prefixes di, tri, tetra etc., used to designate several groups of the same kind • Prefixes are not considered when alphabetizing (Example: dimethyl = m for alphabetizing) • Parent chain goes LAST

1,1,1-trichloro-1fluoromethane

1,1-dichloro-1,1difluoromethane

Structural Formulas • “Lazy” way to write the Hydrogens • Instead of drawing the bonds, just state how many hydrogens are attached • NOTE: The bonds are between CARBONS in a parent chain, and not hydrogens!

Structural Formula Lewis Structure

Order of Priority • IN A TIE, halogens get the lower number before alkyl groups 5

4

3

2

1

4-chloro-2-methylpentane or 2-chloro-4-methylpentane?

Order of Priority • IN A TIE between SIMILAR GROUPS, the group lower ALPHABETICALLY gets the lower number

4-bromo-2-chloropentane or 2-bromo-4-chloropentane ?

Isomers Isomers: Compounds with same molecular formula but different structures.

• Straight chain alkanes: An alkane that has all its carbons connected in a row. •Branched chain alkanes: An alkane that has a branching connection of carbons.

• Petroleum products and the ranges of hydrocarbons in each product.

• There is only one possible way that the carbons in methane (CH4), ethane (C2H6), and propane (C3H8) can be arranged.

• However, carbons in butane (C4H10) can be arranged in two ways; four carbons in a row (linear alkane) or a branching (branched alkane). These two structures are two isomers for butane.

•Different isomers are completely different compounds. They have different structures, different physical properties such as melting point and boiling point, and may have different physiological properties.

• Number of possible isomers increases rapidly with the number of carbons – C30H62 – >4 billion possible isomers

Properties of Alkanes • Main property: will burn

C C C Types of Carbon AtomsH H C C H

• Primary carbon (1o) – a carbon bonded to one other carbon • Secondary carbon (2o) – a carbon bonded to H two other carbons •

H H

C C C C C C H H H Tertiary carbon (3o) H C C – a carbon bonded to H C C C three other carbons H C C C H C C C H

Unsaturated Hydrocarbons • Can have more hydrogen atoms added • Very important in biological systems • Alkene: hydrocarbon that contains one or more carbon-to-carbon double bonds • To show the presence of the double bond, the –ane suffix from the alkane name is changed to –ene. – General formula of CnHn •

Simplest: ethylene, C2H4

• Ethylene is the gas that ripens fruit, and a ripe fruit emits the gas, which will act on unripe fruit. Thus, a ripe tomato placed in a sealed bag with green tomatoes will help ripen them.

Naming of Alkene is similar to naming alkanes except: • The longest continuous chain must contain the double bond. • The base name now ends in –ene. • The carbons are numbered so as to keep the number for the double bond as low as possible. • The base name is given a number which identifies the location of the double bond.

Alkynes • Alkyne: hydrocarbon that contains one or more carbon-tocarbon triple bonds • Naming an alkyne is similar to the alkenes, except the base name ends in –yne. • General formula of CnH2n–2 • Simplest: acetylene, C2H2

Properties of Alkenes and Alkynes • Similar physical properties to alkanes • Undergo more reactions than alkanes – Addition reaction: add compounds across double bond – Importantly, they can form polymers

Cyclic Hydrocarbons • Carbon atom chains in form of rings • Can be represented by structural formulas or symbolic representations

• Cycloalkanes and Aromatic Hydrocarbons – Cycloalkanes are alkanes (only carbon to carbon single bonds) which form a ring structure. • The "straight" chain has carbon atoms that are able to rotate freely around their single bonds, sometimes linking up in a closed ring. • (B) Ring compounds of the first four cycloalkanes.

– An aromatic compound is one that is based on the benzene ring(C6H6). – Structure: Alternating single & Double Bonding

H

H

H

H

H H

–A benzene ring that is attached to another compound is given the name phenyl.

Functional Groups • Group of atoms that gives a family of organic compounds its characteristic chemical and physical properties • Alkyl group: derived from alkane by removing a H – R stands for alkyl group in general

Halogens

– Halogens (F2, Cl2, Br2, I2,) can all add to a hydrocarbon to form am alkyl halide. • When naming the halogen the –ine ending is replaced by –o • Fluorine becomes fluoro • Chlorine becomes chloro • Bromine becomes bromo • Iodine becomes iodo

Common examples of organic halides.

Alcohol Family • –hydroxyl(OH) group • Replace -e with -ol • CH3OH, methanol, simplest • Produced industrially – Mainly a chemical intermediate

• C2H5OH, ethanol • Made industrially and by fermentation – Industrially produced alcohol has noxious substances added

• Small, simple alcohols tend to be toxic

Multifunctional Alcohols • Several common alcohols have more than one –OH group • Ethylene glycol: main ingredient in antifreeze • Glycerol: used in lotions – Ingredent in some explosives

Ethers • Two alkyl groups attached to same O – Example CH3CH2-O-CH2CH3

• Used mainly as solvent • Little chemical reactivity – Insoluble in water – Highly flammable

Aldehydes and Ketones • Both contain carbonyl group (C=O) • Aldehyde: R-CHO • Ketone: R-CO-R’

Common Aldehydes • • • •

Change -e ending to -al Produced by oxidation of alcohols Formaldehyde – used as a preservative Larger ones used as fragrances – Benzaldehyde – flavor in maraschino O cherries

C

H

Common Ketones • Change -e ending to -one • Acetone most common ketone – Used primarily as a solvent

• Produced by oxidation of alcohols

O C H3 C

CH3

Carboxylic Acid • Contains C=O and –OH group on same carbon • Change -e to -oic acid • Acetic acid: acid in vinegar

O

R

C OH

The red ants, like other ants, make the simplest of the organic acids, formic acid. The sting of bees, ants, and some plants contains formic acid, along with some other irritating materials. Formic acid is HCOOH.

Esters • Derived from carboxylic acids and alcohols • Tend to be fragrant – Methyl butyrate – Ethyl butyrate – Ethyl formate – Methyl salicylate

apple pineapple rum wintergreen

Amines • Contain N • May have 1, 2, or 3 alkyl or aromatic groups • Most biological amines are amino acids – Building blocks of proteins

Amides • N bonded directly to carbonyl group • Linkage that holds proteins together

O R '' R

N R'

Heterocyclic Compounds • Ring compounds that have something other than C in the ring • Occur in plants – Alkaloids: basic in solution – Examples: caffeine, morphine, cocaine

• Form basic structure of DNA

CHEMISTRY In Everyday Life

An Annexure Free with Organic Chemistry.Ppt

The Chemical Universe • Chemistry is the study of atoms • Atoms are the building blocks of nature • How many atoms are there in a cup of tea? 15,000,000,000,000,000,000,000,000 Chemical Science is shaping our future

Chemistry of Flowers • Smell a Flower – The Fragrance is Chemistry

• See a Flower – The Colours are Chemistry

• Touch a Flower – The Structure is Chemistry

Chemistry in the Home • Everything in your home is Chemistry • Shower Gel, Wallpaper, Baked Beans… • Teflon™ was discovered by accident • Energy efficient, colour changing buildings

Paints • Pigment – Particles to add colour

• Matte Paints – Particles to add texture

• Non-Drip Paints – Polymers to change consistency

Improved Performance • Our leisure time has been changed by Chemical Science • Computer parts, sports equipment • Carbon fibre is 3 times stronger than steel • Better flat screen displays

Flat Screen Displays • The past – Cathode ray tubes

• The present – Liquid Crystals – Plasma displays

• The future – Light emitting polymers – Electronic Ink

Modern Masters • Art and the Chemical Sciences are linked • Art preservation • Chemistry is art – Sense-ational – Visual Elements

• New materials for artists

Photography • Chemistry makes the film • Chemistry develops the image • Chemistry prints the picture

Cooking is Chemistry • Chemical changes are responsible for changes in flavour and texture • Chemistry keeps food fresh • Most E-numbers are naturally occurring • Healthy Cream Cakes!

Ice Cream • Complex Structure – Ice – Fat – Air – Sugar

• Stability

Energy is Chemistry • Chemistry can be used to store energy • Batteries are chemistry • The Space Shuttle’s solid rockets burn 10 tonnes of fuel per second • Cleaner sources of energy

Petrol • Drilling Fluids • Refining • Fuel Additives • Catalytic Converters

Green Chemistry • Chemical science that is environmentally friendly • More efficient production of the chemicals we need • 53% of people recycle paper - only 23% recycle plastic • Cars powered by hydrogen

Organic Farming • Use of natural pesticides and fertilisers • Chemists isolate, develop and make these • Even organic pesticides are chemicals!

Fashion • Looking good is down to chemical science • 2-in-1 shampoos, non-iron shirts • Toothpaste and paint have many similar ingredients • Self-cleaning clothes

Synthetic Dyes • Desired Colour • Dye fastness • Novel properties

Healthier Lives • All medicines use chemical science • Clean water through chemical science • We live twice as long now as 100 years ago • Cures for Cancer, AIDS…

Asthma Drugs • Container – Plastic shell

• Active Ingredient – Pharmaceutical

• Spray Formation – Aerosol

Image courtesy of GlaxoSmithKline

Biochemistry • Human body is made up of 100 trillion cells • Adult body is 50-65% water • Carbon is key element in the body • 22 amino acid structures

Body chemistry • Proteins-digest foods, fight infections, build organs, move muscles • Enzymes are proteins • Blood and oxygen • DNA-genetic molecule

Chemical Science... • ... is important to us all • … is the world around us … is more than you might have thought • … is always looking to the future

AN AMRITH POWER PRESENTATION

END