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Organic ChemistryCarbon Bonding

AlkanesFunctional Groups

Carboxylic Acids and EstersPolymers

BiochemistryProteinsEnzymes

CarbohydratesNucleic Acids

Lipids

Unit 10 – Chemical of Life

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Unit 10 – Chemical of Life

• Upon completion of this unit, you should be able to do the following:– Describe the types of bonds formed by the carbon

atom.– Name some common alkanes.– Name some common functional groups in organic

molecules.– List four important types of biomolecules.

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Chapters not in book available only website

Sections 19.1, 19.2, 19.10, 19.15 and 19.16Pages 574-579, 598 and 605-610

Sections 20.1, 20.2, 20.5, 20.6, 20.7, 20.8, 20.9Pages 623-624, 628-644

Unit 10 – Chemical of Life

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Organic Chemistry• The study of carbon-containing compounds and

their properties is called organic chemistry• Carbon has the unusual ability of bonding

strongly to itself, forming long chains or rings of carbon atoms.

• Carbon also forms strong bonds to other nonmetals, such as hydrogen, nitrogen, oxygen, sulfur and the halogens

• Because of these bonding properties, an extraordinary number of carbon compounds exist

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Organic Chemistry• A few carbon compounds are considered to be

inorganic, such as oxides and carbonates, but the majority of carbon compounds are designated as organic compounds.

• Originally, the distinction between organic and inorganic substances was based on whether they were produced by living systems.

• This misconception was dispelled in 1828 when Friedrich Woehler prepared urea from the inorganic salt ammonium cyanate by simple heating. Urea is a component of urine, so it is organic, but here it was produced in the lab.

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Organic Chemistry• Organic chemistry is a vast subject so this

presentation will be a brief introduction• Start with an understanding of carbon bonding• Then study a simple class of organic compounds

called the hydrocarbons.

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Carbon Bonding• So many carbon containing compounds exist

because carbon forms strong bonds to itself and to many other elements.

• Carbon has an electron configuration of 1s2 2s2 2p2 or [He]2s2 2p2. It has 4 valence electrons.

• A carbon atom can form bonds to a maximum of four other atoms. These can be carbon atoms or atoms of another element.

• Methane, CH4, is one carbon atom bonded to four hydrogen atoms. It has 8 valence electrons.

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Carbon Bonding

• Carbon can bond to fewer than four elements by forming one or more multiple bonds.

• A multiple bond involves the sharing of more than one pair of electrons

• A double bond involves sharing two pairs of electrons.

• A triple bond involves sharing of three pairs of electrons.

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Carbon Bonding• Ethylene, C2H4, with 12 valence electrons, has a

double bond. In the case of ethylene, the carbon is bound to three other elements.

• An organic molecule with a triple bond is acetylene, C2H2.

H-C Ξ C-H

H

H H

HC=C

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Hydrocarbons• Hydrocarbons are compounds composed of

carbon and hydrogen. Those whose carbon-carbon bonds are all single bonds are said to be saturated because each carbon is bound to four atoms, the maximum number.

• Hydrocarbons containing carbon-carbon multiple bonds are described as being unsaturated because the carbon atoms involved in a multiple bond can bond to one or more additional atoms.

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HydrocarbonsThis is shown by the addition of hydrogen to ethylene.

Ethylene Ethane H H | | C=C + H2 → H – C – C – H | | H H

Unsaturated Saturated

H

H H

H

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AlkanesEach carbon in ethylene is bonded to three atoms, but can bond to one additional atom after one of the carbon-carbon bonds is broken. This forms ethane, a saturated hydrocarbon.

Saturated hydrocarbons are called alkanes. Methane, CH4, is the simplest alkane. The next alkane, containing two carbon atoms is ethane, C2H6. The next two members of the alkane series are propane, C3H8 and butane C4H10.

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Alkanesmethane CH4

ethane C2H6

propane C3H8 butane C4H10

pentane C5H12

hexane C6H14

heptane C7H16

octane C8H18

nonane C9H20

decane C10H22

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Alkanes• Alkanes in which the carbon atoms form long

strings or chains are called normal, straight chain or unbranched hydrocarbons.

• Normal alkanes can be represented by the formula

CH3 – (CH2)m – CH3

This follows a general formula of CnH(2n+2), where n = number of carbon atoms

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Functional Groups• The vast majority of organic molecules contain

elements in addition to carbon and hydrogen. Most of these can be considered hydrocarbon derivatives, molecules that are fundamentally hydrocarbons but have additional atoms or groups of atoms called functional groups.

• The symbols R and R’ represent hydrocarbon groups which may or may not be the same.

• R can be as simple as –H or –CH3

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Common Functional GroupsClass Functional

GroupGeneral Formula Example

Alcohols -OH R-OH CH3-OH

Ethers -O- R-O-R’ CH3-O-CH3

Aldehydes O || -C-H

O || R-C-H

O || H-C-H

Ketones O || -C-

O || R-C-R’

O || CH3-C-CH3

Carboxylic Acids O || -C-OH

O || R-C-OH

O || CH3-C-OH

Esters O || -C-O-

O || R-C-O-R’

O || CH3-C-OCH2CH3

Amines -NH2 R-NH2 CH3NH2

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Carboxylic Acids and Esters• Carboxylic acids are characterized by the presence

of the carboxyl group –COOH.• The general formula for a carboxylic acid is RCOOH.• These molecules typically are weak acids in aqueous

solutions, meaning that little acid dissociates in water. Remember acetic acid.

CH3-COOH (aq) + H2O (l) H3O+ (aq) + CH3-COO- (aq)

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Carboxylic Acids and Esters• A carboxylic acid reacts with an alcohol to form an

ester and a water molecule.RCOOH + R’OH → RCOOR’ + H2O

acid alcohol ester water

• Esters often have a sweet, fruity odor that contrasts markedly with the often pungent odor of the parent carboxylic acid.

• A very important ester is formed from the reaction of salicylic acid and acetic acid. The product is acetylsalicylic acid, more commonly known as aspirin.

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Polymers• Polymers are large, usually chain like molecules

built from small molecules called monomers.• Polymers form the basis for synthetic fibers,

rubbers and plastics.• Many important biomolecules are also polymers.• The simplest synthetic polymer is polyethylene

nCH2=CH2 where n represents a very large number, usually

thousands

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Polymers• Polyethylene is a tough, flexible plastic used for

piping, bottles, electrical insulation, garbage bags and many other purposes.

• The properties of polyethylene can be varied by using substituted ethylene monomers. For example, when tetrafluoroethylene is used as the monomer, the polymer Teflon® is obtained.

H

H H

HC=C

F

F F

FC=C

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BiochemistryProteinsEnzymes

CarbohydratesNucleic Acids

Lipids

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Proteins• Many useful synthetic materials are polymers• Many natural materials are also polymers

including starch, hair, silk, cotton fibers and the cellulose in woody plants

• Proteins are natural polymers that make up about 15% of our bodies

• The building blocks of all proteins are the amino acids. Amino acids have an amine functional group on one end of the polymer chain and a carboxylic acid on the other end of the chain.

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Proteins

• The R in this structure may represent H, CH3 or more complex groups. These R groups are also called side chains.

• Amino acids are grouped into polar and non-polar classes based on the composition of the side chains.

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Proteins

• Non-polar side chains contain mostly carbon and hydrogen atoms.

• Polar side chains contain nitrogen and oxygen atoms• This difference is important because polar side

chains are hydrophilic (water-loving) and non-polar side chains are hydrophobic (water-fearing).

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Proteins

• The protein polymer is built by reactions between amino acids, forming a C-N bond with the elimination of water.

• The product shown above is called a dipeptide.• The peptide linkage or peptide bond is shown below

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Proteins• Additional reactions lengthen the chain to

produce a polypeptide and eventually a protein.

• Twenty amino acids are naturally incorporated into polypeptides and are called proteinogenic or standard amino acids.

• The 20 amino acids can be assembled in any order, allowing for a large number of possible combinations.

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Proteins• The order or sequence of amino acids in the

protein chain is called the primary structure.• The three-dimensional structure of a protein is

crucial to its function.• The process of breaking down this structure is

called denaturation. For example, heat causes the breakdown of egg proteins when an egg is cooked.

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Proteins• Any source of energy can cause the

denaturation of proteins and is potentially dangerous to living organisms.

• Ultraviolet radiation, x-ray radiation or nuclear radioactivity can disrupt protein structure, which may lead to cancer or genetic damage.

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Enzymes• Enzymes are proteins that catalyze specific

biological reactions.• A catalyst is a substance that speeds up a

reaction without being consumed.

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Enzymes• In an enzyme reaction, the reacting molecules

are called substrates. The substrate and enzyme attach to each other in a way that the part of the enzyme where the reaction is to occur occupies the active site of the enzyme.

• After the reaction occurs, the products are liberated and the enzyme is ready for a new substrate.

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Carbohydrates• Carbohydrates are another class of biological

molecules.• They serve as food sources for most organisms.• Many carbohydrates have the empirical

formula of CH2O, so it was thought that they were hydrates of carbon (C H∙ 2O), hence the name.

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Carbohydrates• Carbohydrates are polymers constructed from

molecules called simple sugars, or more precisely, monosaccharides.

• Monosaccharides are aldehydes or ketones that contain several hydroxl (-OH) groups.

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Carbohydrates• An example of a monosaccharide is fructose, a

sugar found in honey and fruits.

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Carbohydrates• More complex carbohydrates are formed by

combining monosaccharides. Two monosaccharides can be combined to form a disaccharide. Sucrose, common table sugar, is formed by combining fructose and glucose.

• Polysaccharides are formed by the combination of many monosaccharides. Starch, cellulose and glycogen are three important polysaccharides.

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Carbohydrates• Starch is the carbohydrate reservoir in plants. It is

the form in which glucose is stored by the plant for later use as a cellular fuel, both by the plants and by organisms that eat the plants.

• Cellulose is a major structural component of woody plants and natural fibers. The structure of cellulose is different that starch. Humans do not have the enzymes required to break down cellulose, but termites, cows and deer do.

• Glycogen is the main carbohydrate reservoir in animals. It is found in uscles where it can be broken down into glucose when energy is required.

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Nucleic Acids• The substance that stores and transmits genetic

information is a polymer called deoxyribonucleic acid (DNA).

• Ribonucleic acid (RNA) is a smaller polymer that also carries information for the synthesis of various proteins the cell requires to carry out its life functions.

• The fundamental unit of both DNA and RNA is a nucleotide.

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Nucleic Acids• Each nucleotide has three parts

1. A nitrogen containing organic base2. A 5-carbon sugar3. A phosphate group

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Lipids• Lipids are a group of substances defined in

terms of their solubility characteristics.• They are water insoluble substances that can be

extracted from cells by organic solvents.• Three are four classes: fats, phospholipids,

waxes, and steroids.

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Lipids• The most common fats are esters composed of

the trihydroxy alcohol known as glycerol and long-chain carboxylic acids called fatty acids.

• Fats that are the esters of glycerol are called triglycerides.

• Triglycerides can be broken down by treatment with aqueous sodium hydroxide. The products are glycerol and fatty acid salts, called soaps. This process is called saponification.

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Lipids• Phospholipids are esters of glycerol that contain

only two fatty acids.• Waxes are esters that involve monohydroxy

alcohols instead of glycerol. They are solids that furnish waterproof coatings on leaves and fruit and on the skins and feathers of animals.

• Steroids are a class of lipids that have a carbon ring structure. They comprise four groups: cholesterol, adrenocorticoid hormones, sex hormones and bile acids.