The chemistry of carbon Unit 8: Organic Chemistry The chemistry of carbon

Organic compounds contain carbon Properties of organic compounds 1. most are insoluble in water (non-polar) 2. most have low melting (weak intermolecular forces) and boiling points 3. most are non-electrolytes (covalent bonds) 4. most reactions are slow (strong covalent bonds)

ALWAYS!!! The Carbon Atom -- has 4 valence electrons -- makes 4 covalent bonds ALWAYS!!! tetrahedron In the structural formula, shared electron pairs are shown by a dash -- can form double and triple bonds

Other atoms often found in organic compounds: H – 1 bond O – 2 bonds N – 3 bonds halogens – 1 bond Some compounds have the same molecular formula, but different structural formulas Example: C2H6O CH3CH2OH CH3OCH3 These are called isomers

Classification of Organic Compounds 1. Is based on the carbon skeleton -- all single C-C bonds saturated -- at least one double or triple C-C bonds unsaturated 2. Is based on the other atoms present -- if only H and C hydrocarbons Families of Organic Compounds Saturated hydrocarbons: are called alkanes

The Alkane Series H CH4 methane | H—C—H CH4 methane See Table P for the first 10 prefixes used in naming organic compounds H H | | H—C—C—H C2H6 ethane H H H | | | H—C—C—C—H C3H8 propane | | | | —C—C—C—C— | | | | C4H10 butane

Alkanes have the general formula CnH2n+2 (Table Q) | | | | | —C—C—C—C—C— | | | | | C5H12 pentane | | | | | | —C—C—C—C—C—C— | | | | | | C6H14 hexane | | | | | | | —C—C—C—C—C—C—C— | | | | | | | heptane C7H16 | | | | | | | | —C—C—C—C—C—C—C—C— octane C8H18 C9H20 nonane C10H22 decane Alkanes have the general formula CnH2n+2 (Table Q)

As the alkanes get larger, the melting pt and boiling pt increase Example: No. of carbons 1 2 3 4 5 6 7 8 9 10 11 12....20.....50 gas liquid oil wax Alkanes with more than 3 carbons have isomers | —C— | | | —C—C—C— | | | | —C—C—C—C— Butane n-butane isobutane | —C— | | | —C—C—C— — C— | —C— | | | | —C—C—C—C—   | | | | | —C—C—C—C—C— | | | | | Pentane n-pentane isopentane neopentane

Standard Nomenclature for Alkanes IUPAC System 1. Names are based on the longest chain of carbons   | — C— | | | | | | —C—C—C—C—C—C— —C—   | — C— | | | | | | —C—C—C—C—C—C—   | — C— | | | | | | —C—C—C—C—C—C—   | — C— | | | | | | —C—C—C—C—C—C— | | | | | | —C— 6 = hexane 7 = heptane 2. Name the carbon branches (end in –yl) methylhexane dimethylheptane

3. Tell location of branches -- assign numbers to carbon atoms in the chain -- branch is on the lowest numbered carbon   C | C—C—C—C—C—C C | C—C—C—C—C—C 5 6 7 1 2 3 4 5 6 1 2 3 4  6 5 4 3 2 1 3-methylhexane 3,5-dimethylheptane

Halides or Halocarbons --where a hydrogen has been replaced by a halogen (F, Cl, Br, I) --same naming rules, branches = fluoro-, chloro-, bromo-, iodo- | —C— | | | | | | —C—C—C—C—C—C— I Br | | | | | —C—C—C—C—C— 2-bromopentane 2-methyl-4-iodohexane Br | | | Cl —C—C—C—Br Cl 1,3-dibromo-1,2-dichloropropane

Alkenes Hydrocarbons with one double bond are called H H H | | / H—C—CC | \ H H named like alkanes, but end in - ene C3H6 = Propene General formula for the alkenes = CnH2n (Table Q) Alkenes with 4 or more carbons have isomers even when unbranched Example : Butene C4H8   H H H H \ | | | CC—C—C—H / | | H H H H H H | | | H—C—CC—C—H | | | H H H To Name: number the carbon atoms as before, so the double bond starts on the lowest numbered carbon

Begin the name with the lowest numbered carbon in the double bond C  C—C—C 1 2 3 4 C—C  C—C 1 2 3 4 Begin the name with the lowest numbered carbon in the double bond 1-butene 2-butene Use the same numbering system for branches Examples: | | | | | | —C—C—C—CC—C—C— | | | | | | —C— | | | | | / Cl—C—C—C—CC | | | \ 5-chloro-1-pentene 5-methyl-3-heptene

Alkynes Hydrocarbons with one triple bond are called named like alkanes, but end in - yne H H | | H—C—C≡C—C—H 2-butyne = C4H6 General formula for the alkynes = CnH2n-2 (Table Q) Example: | | | | —C—C—C—C≡C—C— —C— | 4-methyl-2-hexyne One old name is still widely used: C2H2 = ethyne = acetylene —C≡C—

Other Organic Families --consist of a hydrocarbon in which a H has been replaced by a functional group (Table R) --the functional group determines the compound’s properties and reactions 1. Alcohols functional group: —O—H [not bases: the –OH does not ionize to form OH-] named according to the parent hydrocarbon, but... the –e ending is changed to –ol a number tells where the –OH is, if necessary Examples: OH | | | | | —C—C—C—C—C— | | —C—C—O—H ethanol 2-pentanol

2. Organic Acids functional group: ║ R—C—OH 2. Organic Acids functional group: or R-COOH (R stands for any number of carbons, or just an H) Examples: O ║ H—C—OH O | ║ —C—C—OH | name by parent hydrocarbon …… drop –e, add -oic acid IUPAC: methanoic acid ethanoic acid old: formic aid acetic acid Fatty acids have many-carbon R groups: O | | | | | | | | | | | | | | | | | ║ —C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—C—OH | | | | | | | | | | | | | | | | | saturated O | | | | | | | | | ║ —C—CC—CC—CC—CC—CC—CC—CC—CC—C—OH | | | | | | | | | unsaturated

3. Aldehydes 4. Ketones functional group: ║ R—C—H 3. Aldehydes functional group: naming: drop -e ending, add -al Example: O ║ H—C—H IUPAC: methanal old: formaldehyde O ║ R1—C—R2   4. Ketones functional group: needs at least 3 carbons -- otherwise it’s an aldehyde naming: drop –e ending, add -one O ║ CH3—C—CH3   Example: IUPAC: propanone old: acetone use numbers to indicate position of O, if necessary

5. Ethers 6. Esters functional group: R1—O—R2 Name both R groups as branches, then “ether” Example: CH3—CH2—O—CH2—CH3 diethyl ether O ║ R1—C—O—R2 6. Esters functional group: Name is based on the original acid -- ending is -oate -- extra carbons are named as a branch O | ║ | | | | | —C—C—O—C—C—C—C—C— | | | | | | Example: pentyl ethanoate many esters have pleasant fragrances

Nitrogen-containing families 7. Amines functional group R1—N—R3 | R2 (often R2 and R3 are H’s making –NH2) name longest carbon chain; drop –e, add -amine | | | / —C—C—C—N | | | \ Example: 1-propanamine 8. Amides O R2 ║ | R1—C—N—H functional group (R2 often = H) name: drop –e, add -amide Example: O H | | | ║ | —C—C—C—C—N—H | | | butanamide

9. Amino Acids (NOT on Table R but need to know) have the amine and acid groups O \ | ║ N—C—C—O—H / | R Different R groups create 20 different amino acids Amino acids join together in long chains to form proteins

Reactions of Organic Compounds are usually slow 1. Substitution -- replacing the H of an alkane with a halogen Example: H H H | | | H—C—C—C—Cl H H H | | | H—C—C—C—H + Cl2  + HCl C3H8 C3H7Cl Result: a mixture of isomers – the Cl can replace any H

2. Addition Example: + Cl2  -- adding 2 halogen atoms at the site of a multiple bond Example: H H H | | | H—C—CC—C—H | | | H H H H H Cl H | | | | H—C—C—C—C—H H Cl H H + Cl2  C4H8Cl2 C4H8 Result: one particular isomer Reactivity: alkynes › alkenes › alkanes F2 › Cl2 › Br2 › I2

When hydrogen is added, the compound becomes saturated. H H | | C C H H H H | | H—C—C—H   H2 +  This is called hydrogenation 3. Fermentation Changes sugar  alcohol C6H12O6  2 C2H5OH + 2 CO2 glucose  ethanol + carbon dioxide uses enzymes, from yeast, as catalysts

4. Esterification alcohol + acid  water + ester  HOH ║ R—O—C—R— O ║ OH—C—R—  HOH + R—OH + since water is removed, this is an example of a condensation, or dehydration, reaction Fats are esters of glycerol and fatty acids glycerol + 3 fatty acids  fat + 3 water O ║ —C—O—C—C—C—etc | O | ║ O ║ OH—C—C—C—etc | —C—OH O ║ OH—C—C—C—etc + 3 HOH O ║ OH—C—C—C—etc

5. Saponification The breakdown, or hydrolysis, of an ester ester + base  alcohol + salt of organic acid (soap) O ║ NaO—C—C—C—etc O ║ —C—O—C—C—C— | O | ║ Ex. | —C—OH + + NaOH O ║ NaO—C—C—C—etc + NaOH O ║ NaO—C—C—C—etc + NaOH fat + 3 base  glycerol + 3 soap

6. Combustion a. if O2 is abundant: complete combustion hydrocarbon + oxygen  carbon dioxide + water Ex. CH4 + 2O2  CO2 + 2H2O b. if O2 is scarce, or at lower temps: incomplete combustion Ex. 2CH4 + 3O2  2CO + 4H2O Ex. CH4 + O2  C + 2H2O

7. Polymerization the joining together of many small molecules (monomer) to form a large, chain-like molecule (polymer) Examples: chain of sugar molecules = chain of amino acids = protein starch, or cellulose rubber, plastics, natural and synthetic fibers cotton, wool nylon, polyester

[ ] 2 types of polymerization: A. Condensation polymerization --produces water as a product Example: H H O | | ║ H—N—C—C—OH | R H H O | | ║ H—N—C—C—OH | R H H O | | ║ H—N—C—C—OH | R amino acids HOH HOH [ ] H H O H H O H H O | | ║ | | ║ | | ║ H—N—C—C—N—C—C—N—C—C—OH | | | R R R H H O | | ║ —N—C—C— | R OR n protein

[ ] B. Addition Polymerization -- monomer must be unsaturated Example: H H | | CC H Cl H H | | CC H Cl H H | | CC H Cl chloroethene (vinyl chloride) [ ] | | | | | | —C—C—C—C—C—C— Cl Cl Cl | | —C—C— Cl polychloroethene (polyvinyl chloride) or n