Organic Chemistry, 5th Edition L. G. Wade, Jr. Chapter 1 Introduction and Review ORGANIC CHEMISTRY STUDY OF CARBON-CONTAINING Chapter 1 COMPOUNDS 2 SHORT HISTORY OF CHEMISTRY PRE-1828 ERA TWO MAJOR DISCIPLINES EMERGING INORGANIC - MINERAL CHEMISTRY ORGANIC CHEMISTRY - PLANTS AND ANIMALS Chapter 1 3 Classification of Matter CLASSIFICATION OF MATTER FIRE AGE - BASED ON COMBUSTION COMBUSTIBLES - FUELS FROM ANIMALS AND PLANTS OIL, WOOD, FAT NON-COMBUSTIBLES -DIDN Õ T BURN; PUT OUT FIRES SAND, WATER, ROCKS Chapter 1 4 BERZILIUS’ DEFINITIONS ORGANIC COMPOUNDS CHARACTERISTIC PRODUCTS OF LIVING ORGANISMS SUBSTANCES LIKE SUGAR AND OLIVE OIL INORGANIC COMPOUNDS PRODUCTS FROM NON-LIVING ENVIRONMENT SUBSTANCES LIKE WATER AND IRON Chapter 1 5 Vital Force Theory INORGANIC MATERIALS COULD BE CONVERTED TO ORGANIC MATERIALS IN THE PRESENCE OF A VITAL FORCE FOUND ONLY IN LIVING BODIES. Chapter 1 6 Organic Little Studied In addition to Vital Force Theory Organics hard to purify Appeared to violate the Law of Definite Proportions Isomerism problem - same molecular formula but Different compounds Consider ethanol and dimethyl ether Chapter 1 7 1828 Woehler’s urea synthesis Ammonium isocyanate + heat ------> urea NH4CNO NH2CONH2 “I have been able to make urea without aid of kidney of man or dog. 1828 Chapter 1 8 Deutsche Museum Chapter 1 9 STYLES Chapter 1 10 Schubert Chapter 1 11 Liszt - Young Chapter 1 12 Lola Montez Chapter 1 13 Liszt - Old Chapter 1 14 BIRTHS JULES VERNE - AROUND THE WORLD IN 80 DAYS LEO TOLSTOY - ANNA KORNINA, KREUTZER SONATA HANS CHRISTIAN ANDERSON WANG TAO - CHINESE SELF-STRENGTHENING MOVEMENT AMEER MINAI - INDIAN SONG WRITER - AAHISTAA MARRIAGES BARTHOLOMEW HEIFNER AND POLLY GRISHAM. IN SHELBY COUNTY, ENGLAND Chapter 1 15 Wang Tao Attempted to bring China into the 19th Century Was put to death Chapter 1 16 IMPORTANT EVENTS ANDREW JACKSON ELECTED PRESIDENT OF USA DEFEATED JOHN Q. ADAMS RUSSO-PERSIAN WAR ENDED FATH ‘ALI SHAH’ AND RUSSIAN COUNTERPART SIGNED TURKMANCHAI TREATY GAVE RUSSIA - GEORGIA, ARMENIA, AND AZERBAIJAN Chapter 1 17 Post 1828 •Over 18,000 million compounds have been synthesized •Pharmaceuticals •Biochemicals •Plastics •Agrichemicals •Paints Chapter 1 18 Why so many organic? FORMS COVALENT BONDS WITH NON-METALS H O N X P S Se FORMS COVALENT BONDS WITH MANY METALS Li Mg Al Cd Chapter 1 Fe 19 AND WITH ITSELF C C C C C C CH C C C C CH C C C C C C CHAINS CHAINS WITH BRANCHES RINGS No limit Chapter 1 20 Atomic Structure • protons, neutrons, and electrons • isotopes 12 C 6 14 6 C => Chapter 1 21 Atomic Orbitals 2s orbital (spherical) 2p orbital Chapter 1 => 22 Electronic Configurations • Aufbau principle: Place electrons in lowest energy orbital first. • Hund’s rule: Equal energy orbitals are halffilled, then filled. => Chapter 1 23 Table 1-1 Chapter 1 24 => Bond Formation • Ionic bonding: electrons are transferred. • Covalent bonding: electron pair is shared. => Chapter 1 25 Lewis Structures • Bonding electrons • Nonbonding electrons or lone pairs H H C O H H Satisfy the octet rule! Chapter 1 => 26 TIPS • Neutral atoms Carbon 4 bonds (double bonds count as 2 triple bonds count as 3) and NO lone pairs. Nitrogen 3 bonds and one lone pair Oxygen 2 bonds and two lone pairs BORON 3 bonds BUT no lone pairs One who writes MORE than 3 bonds about a neutral BORON is a MORON Chapter 1 27 TIPS2 C - H + + H N H H - C + H + N H H -H+ -H+ C N H + O H +H + O Chapter 1 -H+ O 28 Multiple Bonding => Chapter 1 29 EXAMPLES CO2 SO2 C2H3N C3H6O isomer problem Chapter 1 30 Dipole Moment • Amount of electrical charge x bond length. • Charge separation shown by electrostatic potential map (EPM). • Red indicates a partially negative region and blue indicates a partially positive region. H H C C H H => Chapter 1 31 Electronegativity and Bond Polarity Greater EN means greater polarity => Chapter 1 32 EXAMPLES OF BOND POLARITY C------Br Br--------Cl C-------Li C-------N Chapter 1 33 Calculating Formal Charge • • • • For each atom in a valid Lewis structure: Count the number of valence electrons Subtract all its nonbonding electrons Subtract half of its bonding electrons 3- H O O H C C O O P O H Chapter 1 O => 34 EXAMPLES C2H3O HONH3 + Chapter 1 35 Ionic Structures H H H C N H H H X Na O CH3 + - Cl + or Na _ O CH3 => Chapter 1 36 Resonance - More than one Lewis Diagram Acetate ion -1 O C H C H O H O :N O Chapter 1 Example=> 37 Resonance Example _ _ O • • • • _ O O O N N N O O O O O Consider writing Lewis structure for NO3-2 The real structure is a resonance hybrid. All the bond lengths are the same. Each oxygen has a -1/3 electrical charge. => Chapter 1 38 Resonance Rules Must be legitimate Lewis structures CH3 CH3 - H3C N CH2 + CH3 H3C N CH2 CH3 NO NO Pentavalent nitrogen atom!! Chapter 1 39 • Only electrons can be moved (usually lone pairs or pi electrons). Chapter 1 40 Resonance structures? O O :N :N O H H C H O O OK H C H H NO NO OH H Chapter 1 41 Nuclei positions and bond angles remain the same. C=C-C+ +C-C=C CAN”T SAY “if you turn one around 180o you would End up with same structure” Doing so would violate this rule Chapter 1 42 The number of unpaired electrons remains the same .. H C CH 3 . . H C CH 3 3 3 NO NO Chapter 1 43 DELOCALIZATION OF CHARGE USUALLY IS STABILIZING Delocalization of charge results in fractional charges at alternate atoms Chapter 1 44 Major Resonance Form • has as many octets as possible. • has as many bonds as possible. • has the negative charge on the most electronegative atom. • has as little charge separation as possible. Example=> Chapter 1 45 Major Contributor? H + H C N H H H + H C N H H major minor, carbon does not have octet. => Chapter 1 46 Other Examples Chapter 1 47 Chemical Formulas H O • Full structural formula (no lone pairs shown) H C C O H H O • Line-angle formula OH • Condensed structural formula • Molecular formula • Empirical formula Chapter 1 CH3COOH • C2H4O2 • CH2O => 48 BrØnsted-Lowry Acids and Bases • Acids can donate a proton. • Bases can accept a proton. • Conjugate acid-base pairs. O CH3 acid C OH O + CH3 NH2 CH3 C O - conjugate base base + CH3 + NH3 conjugate acid => Chapter 1 49 EXAMPLES BASE CH3CO2H + CONJ ACID :NH3 CH3CO2CONJ BASE ACID + OH O: + H3C OH + NH4+ H2SO4 H3C + -HSO4 OH Amphoterism - ability to behave as an acid or base Chapter 1 50 Acid and Base Strength • • • • Acid dissociation constant, Ka Base dissociation constant, Kb For conjugate pairs, (Ka)(Kb) = Kw Spontaneous acid-base reactions proceed from stronger to weaker. O CH3 C OH pKa 4.74 O + CH3 NH2 pKb 3.36 CH3 C O - pKb 9.26 + CH3 + NH3 pKa 10.64 => Chapter 1 51 EXAMPLES Will NaOH neutralize phenol (C6H5OH)? NaOH + C6H5OH HOH + C6H5ONa pKa = 10 pKa = 15.7 YES!! Stronger acid _ -OH + C6H5OH Weaker acid + C6H5OHOH Chapter 1 52 Determining Relative Acidity • Electronegativity • Size • Resonance stabilization of conjugate base => Chapter 1 53 Electronegativity As the bond to H becomes more polarized, H becomes more positive and the bond is easier to break. => Chapter 1 54 Size • As size increases, the H is more loosely held and the bond is easier to break. • A larger size also stabilizes the anion. => Chapter 1 55 Resonance • Delocalization of the negative charge on the conjugate base will stabilize the anion, so the substance is a stronger acid. • More resonance structures usually mean greater stabilization. O CH3CH2OH < CH3C OH O < CH3 S O Chapter 1 OH => 56 Lewis Acids and Bases • Acids accept electron pairs = electrophile • Bases donate electron pairs = nucleophile CH2 CH2 nucleophile + BF3 electrophile _ BF3 CH2 + CH2 => Chapter 1 57 End of Chapter 1 Chapter 1 58