Presentation on theme: "Chapter 1 Structure and Bonding I.What is Organic Chemistry? A.Organic Chemistry = chemistry of carbon containing (organic) molecules B.Most Familiar compounds."— Presentation transcript:
Chapter 1 Structure and Bonding I.What is Organic Chemistry? A.Organic Chemistry = chemistry of carbon containing (organic) molecules B.Most Familiar compounds are “organic” 1)Cotton in clothing4) Plastics 2)Gasoline5) Drugs 3)Food6) Dyes C.Natural Products vs. Synthetic Organic compounds 1)Natural Products are compounds we find in the environment a)May need to be refined or isolated from the source b)Are starting materials for synthetic compounds 2)Synthetic Organic compounds do not occur naturally and must be synthesized from simpler compounds D.Caffeine: an important organic molecule
In 1998, Americans guzzled 15 billion gallons of soda, an average of about 585 cans per person. Caffeine in sodas aims to addict, study suggests Researchers draw comparison to nicotine’s use in cigarettes MSNBC Staff and Wire Reports 8/15/00 Select an addictive substance from the menu below to read about the psychological and physical effects each drug has on the human body. Source: 'Principles of Addiction Medicine', 1994 Caffeine is the world’s most widely consumed and only entirely unregulated psychoactive agent. It works by blocking a sedating compound in the brain. Blood levels peak within 30 to 45 minutes, and withdrawal symptoms -- including headache, fatigue and an inability to concentrate -- set in after 12 to 24 hours. About 10 percent of the population develops a dependence syndrome called caffeinism, which is indistinguishable from panic disorder or general anxiety. The more caffeine you consume, the more likely you are to use anti- anxiety medications. Fatal oral overdoses are extremely rare, requiring the consumption of 50 to 100 cups of regularly brewed coffee. Caffeine in soft drinks — which Americans drink more of than water — is added to addict consumers, not to enhance flavor as soft drink manufacturers claim, said researchers who compared caffeine’s use in sodas to nicotine in cigarettes. http://www.msnbc.com/news/446035.asp?bt=nm&btu=http://www.msnbc.com/tools/newstools/d/news_menu.asp&cp1=1
Course Overview II.How will we study Organic Chemistry A.Relationship of a molecule’s Structure with its Reactivity B.Functional Group = a group of atoms that controls a molecule’s reactivity 1)Method of classifying organic molecules 2)Similar reactivity for compounds having the same functional group C.Nomenclature = systematic naming of organic compounds D.Reactivity 1)How to synthesize a functional group 2)The reactions a functional group can undergo 3)Mechanism = detailed intermediate steps in a reaction AlkaneAlcohol Ester
Course Overview 2 Text: Reactions are like WordsNeed Both to Mechanisms are like Grammar“Speak” Organic Chemistry E. Stereochemistry = exact arrangement in space of the atoms in a molecule F. Synthesis = making molecules from simpler starting materials
Simple Bonding III. Coulomb Forces as a Simple Bonding Model A.Chemical Bond = energetically favorable interaction of 2 atoms which holds them together at a defined distance from each other 1)Energy (heat) is released as 2 atoms come together to form a bond (energy input is required to break a chemical bond) a)Opposite charges attract b)Electrons spread out to fill a defined space Covalent Bond = shared electrons Ionic Bond = transferred electrons
B. Coulomb’s Law is a basis for chemical bonding Bond Length = distance between nuclei at minimum energy
IV. The Octet Rule A.Periodic Table Review 1)Atomic Number = # of protons = # of electrons in neutral atom 2)Electron Shells: 2, 8, 18, … 3)Valence Shell = outermost shell a)Filled electron shells are energetically desirable so atoms react accordingly b)Noble gases (He, Ne, Ar, Kr, Xe) have filled shells, are unreactive c)Duet important for H, He d)Octet important for C, N, O, …
B. Pure Ionic Bonds 1)Transfer of valence electrons from one neutral atom to another creates a cation and and anion and forms an ionic bond 2)Ionization Potential = energy input to remove an electron Na Na + + e - E = 119 kcal/mol 3)Electron Affinity = energy released upon binding an electron 4)Formation of an Ionic Bond Cl + e - Cl - E = -83 kcal/mol Na + Cl Na+Cl- Ionization Potential = +119 kcal/mol Electron Affinity = -83 kcal/mol Coulomb Attraction = -120 kcal/mol Total E = -84 kcal/mol
C. Electron Dot Notation 1)Core Configuration: Atomic symbol = nucleus + inner shell electrons 2)Valence Electrons: represented by dots around the core 3)Types of Hydrogen a)Hydrogen atom b)Proton c)Hydride D. Covalent Bonds 1)Sharing Electrons to reach octet configuration forms a bond 2)Why aren’t all bonds ionic?
3) Sharing reduces charge and maximizes e- exchange 4)Unequal Sharing gives Polar Covalent Bonds a) Electropositive = electron donating atoms (Na, K, left side of P.T.) b) Electronegative = electron accepting atoms (Cl, N, O, right side P.T.) H 2.2 Li 1.0 Be 1.6 B 2.0 C 2.6 N 3.0 O 3.4 F 4.0 Na 0.9 Mg 1.3 Al 1.6 Si 1.9 P 2.2 S 2.6 Cl 3.2 K 0.8 Br 3.0
c) Ionic Bonds form between extremes d)Covalent Bonds form between like electronegativities e)A Polar Covalent Bond is one between unequal electronegativities f)Symmetry can cancel out the dipole moment for the whole molecule even if the individual bonds are polar
VSEPR Theory E) Valence Shell Electron Pair Repulsion: VSEPR 1) Shape of molecules is determined by repulsion between valence electrons a)Diatomic molecules are linear b)Triatomic molecules can be linear or bent c)AB 3 molecules d)AB 4 molecules Linear Trigonal Tetrahedral
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