C HAPTER 10--A LKANES Dr. Ellen Wilson, RPh, PhD CHE1230

W HY A RE T HERE S O M ANY O RGANIC C OMPOUNDS ?

W HY ARE THERE SO M ANY C ARBON C OMPOUNDS ? Carbon forms stable, covalent bonds with other carbon atoms What does this mean?

T YPES OF BONDING Sharing of electrons CH 3 CH 2 CH 2 CH 2 CH 3 Organic chemistry bonding Partial charges & dipole moments Discrete molecules Dissolve but don’t dissociate Nonelectrolytes Transfer of electrons Na + + Cl - = NaCl Inorganic chemistry bonding Full charges, ions Lattice structures Dissociate in water Electrolytes Covalent BondingIonic Bonding

W HY A RE T HERE S O M ANY O RGANIC C OMPOUNDS ? Carbon forms stable, covalent bonds with other atoms such as H, O, N, S, and halogens

W HAT IS A F UNCTIONAL G ROUP ? A specific group of atoms within a molecule that help define the properties and reactivity of the molecule Will have the same properties regardless of the molecule to which it is attached

C OMMON F UNCTIONAL G ROUPS See inside back cover of text for these examples and more….

F UNCTIONAL G ROUPS M AKE A B IG D IFFERENCE ButanePentaneButanol GasLiquid BP=-0.5 o C36.1 o C o C Insoluble in waterSoluble

F UNCTIONAL G ROUPS G IVE U NIQUE P ROPERTIES Many biologically active molecules are esters, ethers, carboxylic acids, and amines

F UNCTIONAL G ROUPS A LLOW U S TO P REDICT P ROPERTIES OF M OLECULES All alcohols will have the same general properties All amines will have the same general properties All carboxylic acids will have the same general properties Even within a larger molecule, the functional group will have predictable properties even if they are not the properties of the entire molecule

W HY A RE T HERE S O M ANY O RGANIC C OMPOUNDS ? Carbon can form double and triple bonds with other carbon atoms or other atoms

W HY A RE T HERE S O M ANY O RGANIC C OMPOUNDS ? The number of ways that carbon and other atoms can combine is almost limitless

T WO COMPOUNDS CAN HAVE EXACTLY THE SAME MOLECULAR FORMULAS BUT HAVE DIFFERENT PROPERTIES BASED ON THE ARRANGEMENT OF THE ATOMS

Each of the statements given below is true but John Dalton may have had trouble explaining them with his atomic theory. Give explanations for each of the following statements: ethyl alcohol and dimethyl ether have the same composition by mass—52% carbon, 13% hydrogen, and 35% oxygen. However, they have different melting points, boiling points, and solubility in water.

C OMPOUNDS THAT HAVE THE SAME MOLECULAR FORMULA BUT DIFFERENT STRUCTURAL FORMULAS ARE CALLED STRUCTURAL ISOMERS

I N LAB, YOU HAVE ALREADY DISCOVERED SOME OF THE PROPERTIES OF HYDROCARBONS W HAT MAKES THE PHYSICAL PROPERTIES OF HYDROCARBONS DIFFERENT FROM THE PHYSICAL PROPERTIES OF INORGANIC COMPOUNDS ?

B ONDING M AKES THE D IFFERENCE Sharing of electrons CH 3 CH 2 CH 2 CH 2 CH 3 Organic chemistry bonding Partial charges & dipole moments Discrete molecules Dissolve but don’t dissociate Nonelectrolytes Transfer of electrons Na + + Cl - = NaCl Inorganic chemistry bonding Full charges, ions Lattice structures Dissociate in water Electrolytes Covalent BondingIonic Bonding

H OW D O M ELTING /B OILING P OINTS D IFFER ? Low MP and BPHigh MP and BP Organic CompoundsInorganic Compounds

H OW D OES S OLUBILITY D IFFER ? Often insoluble in water Why? Why not? Soluble in water Why? Organic CompoundsInorganic Compounds

H OW D O R EACTION R ATES D IFFER ? Often slow to reactMuch easier to reacteasier Organic CompoundsInorganic Compounds

C OMPARISON Type of bonding? BP = -164 o C MP = -182 o C Slightly soluble in water Flammable Slow to react Can be S, L or G Nonelectrolyte Type of bonding? BP = 1433 o C MP = 801 o C 36g/100mL water Nonflammable Quick to react Exists at S at RT Electrolyte METHANENaCl

O VERVIEW OF H YDROCARBONS Hydrocarbonsaliphatic Alkanes &cycloalkanes alkenesalkynesaromatic

W HAT ARE A LKANES ? Saturated Base molecule contains only C and H No double or triple bonds

T HE F IRST F OUR A LKANES Methane, ethane, propane, butane CH 4, C 2 H 6, C 3 H 8, C4H 10

A M OLECULAR F ORMULA CH 4, C 2 H 6, C 3 H 8, C 4 H 10 GIVES THE TYPE AND NUMBER OF ATOMS IN THE COMPOUND BUT TELLS NOTHING ABOUT THE STRUCTURE OF THE COMPOUND

A S TRUCTURAL F ORMULA GIVES THE ACTUAL ARRANGEMENT OF THE ATOMS IN A MOLECULE

A C ONDENSED F ORMULA REPRESENTS THE ARRANGEMENT OF THE ATOMS WITHOUT DRAWING ALL THE BONDS CH 4 CH 3 CH 3 CH 2 CH 3 CH 3 CH 2 CH 2 CH 3

S TRUCTURAL AND C ONDENSED F ORMULAS A RE E SPECIALLY U SEFUL W HEN D EALING W ITH S TRUCTURAL I SOMERS C 4 H 10 CH 3 CH 2 CH 2 CH 3 C 4 H 10 (CH 3 ) 3 CH butaneisobutane

R EMEMBER, R EMEMBER, R EMEMBER …… C ARBON FORMS 4 BONDS H YDROGEN FORMS 1 BOND

S TRUCTURAL AND C ONDENSED F ORMULAS A RE E SPECIALLY U SEFUL W HEN D EALING W ITH I SOMERS C 5 H 12 CH 3 CH 2 CH 2 CH 2 CH 3 C 5 H 12 CH 3 CH(CH 3 )CH 2 CH 3 pentaneisopentane

PRACTICE: Write the structural formulas from the following condensed formulas : CH 3 CH 2 C(CH 3 ) 3 (CH 3 ) 3 CC(CH 3 ) 3 (CH 3 ) 3 CBr

PRACTICE: Write the condensed formulas from the following structural formulas :

N OMENCLATURE OF A LKANES NAME the parent compound The first TEN straight chain alkanes are: Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane

N OMENCLATURE OF A LAKNES NUMBER the parent compound Find the longest chain Start numbering so that any substituents get the lowest number possible

R EPRESENTATIVE S UBSTITUENTS --CH 3 --CH 2 CH 3 --CH 2 CH 2 CH 3 --CH 2 CH 2 CH 2 CH 3 --CH 2 CH 2 CH 2 CH 2 CH 3 --F --Br --Cl --I

E XAMPLES : Name & number the longest continuous carbon chain Name and number the substituent

E XAMPLES : Name & number the longest continuous carbon chain Name and number the substituent

E XAMPLES : Name & number the longest continuous carbon chain Name and number the substituent

M ORE E XAMPLES : Name & number the longest continuous carbon chain Name and number the substituent

M ORE E XAMPLES : Name & number the longest continuous carbon chain Name and number the substituent

R EACTIONS OF A LKANES Combustion An alkane + oxygen gives carbon dioxide plus water An important side reaction?

R EACTIONS OF A LKANES Halogenation —an alkane plus a halogen gives an alkyl halide (substituted alkane) plus a hydrogen halide (acid) CH 4 + Br 2 → CH 3 -Br + HBr CH 3 CH 3 + Cl 2 → CH 3 CH 2 -Cl + HCl

I S YOUR C YCLOALKANE A BOAT OR A CHAIR?

I S Y OUR H YDROGEN A XIAL OR E QUATORIAL ?