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lec 1 - Welcome to Chem 221 Fundamentals in Organic...

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Unformatted text preview: Welcome to Chem 221 Fundamentals in Organic Chemistry MTuWTh 1:00 ­2:35 exclusively online hAps://chemmac1.usc.edu/221/ How will this class benefit me? •  Studies show that students who complete a class like 221 do beAer in organic chemistry. •  Some USC professors skip material covered in this course because they assume you learned it in 105. Chem 221: Course InformaOon •  General InformaOon –  Instructors –  Lectures –  Virtual Office Hours •  CompuOng Requirements •  Materials •  AAendance •  Grading –  Polling –  Homework –  Quizzes –  Final Exam •  BulleOn Board •  Students with DisabiliOes •  Important Dates •  TentaOve Schedule Chem 221: General InformaOon Credit: 2 units, P/NP; this course cannot be taken for major or general educaCon credit •  Virtual Office hours will be held exclusively online using a department ­developed video chat program. •  To parOcipate, log in to hAp://chemmac1.usc.edu/221/o`ours/student.php during scheduled office hours. Dr. Rebecca Broyer Dr. Thomas Bertolini •  [email protected] •  VOH: Mondays and Wednesdays 2:35 ­4 pm PST •  [email protected] •  VOH: Mondays and Wednesdays 2:35 ­4 pm PST Chem 221: CompuOng Requirements •  An internet connecOon and Flash are required. •  Webcam, headset and microphone are recommended for increased interacOvity during office hours. •  Some graded materials will be submiAed via the course website –  Download a program to draw chemical structures or be equipped with scanning equipment in order to upload hand ­drawn structures. –  See course webpage for compuOng details •  Web/Technical Issues: –  Dr. Bruno Herreros, h[email protected] Chem 221: Materials •  There is no required textbook for this class. •  All materials will be provided online •  OpConal Materials –  Organic Chemistry I: As A Second Language Klein –  Molecular Modeling Kit Chem 221: AAendance •  Any student remaining on the roll sheet aber the last day to drop, July 25, 2011, must accept a grade (Credit or No Credit) and may not be assigned a grade of W. •  There will be no make ­ups for missed assignments unless you make prior arrangements with the instructor. •  Students who miss three or more assignments automaOcally receive a grade of No Credit for the course regardless of their performance. Chem 221: Grading •  •  •  •  •  In ­class assignments Homework Quizzes Final Exam Total: 16 classes @ 5 points 80 points 11 assignments @ 20 points 220 points 4 quizzes @ 40 points 160 points 100 points 560 points •  You must earn 330 points in order to pass this class. Chem 221: Polling •  Daily in ­class parOcipaOon will be monitored using our polling system •  Responses will only be recorded if you are logged ­in live during the class. •  You will not be awarded points if you view the video of the lecture at a later 6me. •  Can I sOll pass the class if I watch the lectures later? Chem 221: Homework •  Homework is assigned daily to help you apply the skills learned in lecture that day. •  Homework assignments may be opened at the end of lecture and must be submiAed to the class website by 2:30pm PST the following day. •  Homework MUST be submiAed online via the course webpage. •  Homework submiAed aber the deadline will be deducted 5 points per day. •  Late HW will not be accepted 3 days past their due date. Chem 221: Quizzes •  Weekly web quizzes will be given to assess your understanding of course material. •  Quizzes open on Mondays and must be completed by Friday at 11:59 pm PST. •  Once you open a webquiz you have only 30 minutes to complete it and may not log on to it again. Chem 221: Final Exam •  The final exam will be administered online Friday August 5, 2011 from 1:00 pm ­3:00 pm PST. •  You must be logged in at this Cme only in order to take the exam. •  The format of the final exam has not been completed, but may require a scanner or chemical drawing sobware. Chem 221: BulleOn Board •  A bulleOn board is available to post quesOons about course material. •  Please use it to post quesOons regarding course material at any Ome so that all students can benefit from your quesOons. •  Please be reminded that this is a public forum and personal maAers should be directed to instructors by email. •  Instructors will post a reply to student quesOons within 24 hours. Chem 221: Students with DisabiliOes •  Any student requesOng academic accommodaOons based on a disability is required to register with Disability Services and Programs (DSP) each semester. •  A leAer of verificaOon for approved accomodaOons can be obtained from DSP. •  Please be sure the leAer is delivered to Dr. Broyer or Dr. Bertolini as early in the semester as possible. •  DSP is located in STU 301 and is open 8:30 a.m.–5:00 p.m., Monday through Friday. •  The phone number for DSP is (213) 740 ­0776. Chem 221: Important Dates •  Last day to Add: Thursday, July 14, 2011 •  Last Day to Drop Class without a Grade of “W” Thursday, July 14, 2011 •  Last Day to Drop Class with a Grade of “W”: Monday, July 25, 2011 •  Final ExaminaOon: online Friday August 5, 2011 1:00 pm ­3:00 pm PST Chem 221: TentaOve Schedule QuesOons? Lewis Structures Chem 221 Monday July 11, 2001 Organic Chemistry Organic chemistry is the chemistry of compounds containing carbon. The name mistakenly implies that all organic compounds are associated with living systems. While many carboncontaining compounds are the basis of life, there are many organic compounds that have nothing to do with living systems. The practice of organic chemistry goes back thousands of years. A discovery of a wine residue in a Sumerian jug shows that the technology of winemaking is almost 7500 years old. sugar (C12H22O11) sweet principle of sugar cane fermentation ethyl alcohol (C2H5OH) Chemical Bonds Two types of chemical bonds were recognized: (A) Ionic bonds are formed by the transfer of one or more valence-level electrons from one atom to another. (B) Covalent bonds are formed when atoms share valence-level electrons. Both types of bonds lead to electronic configurations around atoms that mimic a noble gas--filled outermost electronic levels. Ionic Bonds When atoms lose or gain electrons, they develop charges and are called ions. Positively charged ions are cations, and negatively charged ions are called anions. Li+ lithium cation Ffluoride anion Electronegativity Electronegativity measures the tendency of an atom to attract electrons. Electronegativity increases in going left to right across a row in the Periodic Table. In some groups, it decreases in going down a column. Group 7 Row 2 F decreasing Cl increasing electronegativity electronegativity Br Ionic bonds are formed when atoms of I very different electronegativities interact. Li Be B C N O F most electronegative least electronegative Linus Pauling (1901-1994) Nobel Prize in Chemistry 1954 Nobel Peace Prize 1962 QUESTION 1 List the following atoms in decreasing electronegativity. 1. C > Br > O > F 2. F > O > C > Br 3. F > O > Br > C 4. F > C > O > Br Electronegativity and Types of Chemical Bonds The electronegativity difference between interacting atoms determines the type of bond that is formed. compound electronegativity difference type of bond F2 4.0 - 4.0 = 0 nonpolar covalent HF 4.0 - 2.1 = 1.9 polar covalent LiF 4.0 - 1.0 = 3.0 ionic Lithium Fluoride Li +F + Li + electron configuration of helium Lithium, a metal has very low electronegativity Fluorine, a nonmetal, has very high electronegativity F electron configuration of neon Covalent Bonding When two atoms of the same or similar electronegativities react, they achieve a noble gas electron configuration by sharing electrons in covalent bonds. A two electron bond is shown by a dash or line. Examples H2 CH4 H. + H. . . C. + H. . QUESTION 2 Identify the compound with ionic bonding. 1. CH4 2. NaBr 3. CH3Cl 4. CH3OH Multiple Covalent Bonds and the Octet Rule Covalent bonds between atoms may involve 4 or 6 electrons. These are called multiple covalent bonds. Example N2 Each nitrogen atom has 5 outermost or valence-level electrons. . : N. . The covalent bonding in N2 involves 6 electrons: Now have an octet of electrons in the valence level The Octet Rule The tendency to reach 8 electrons in the valence level Examples of the Octet Rule :N: : : N: H:O:H nitrogen water :: :: :: H H :C: H H methane H:F: hydrogen fluoride These are called Lewis structures. All the valence ­level (outermost) electrons are shown as dots The chemical symbol with the valence ­level electrons shown as dots Example CH3F methyl fluoride The Lewis structures of the atoms are: :: . . C. . F: . H. H. H. The four covalent bonds to the central carbon atom account for 8 of the valence electrons: The remaining 6 valence electrons are nonbonding electrons around the fluorine atom. The octet rule applies to both the carbon and fluorine atoms. Lewis Structures of Ions The Lewis structure of an ion is constructed from the atomic components, but with electrons added or subtracted to achieve the required charge. Example CO32- carbonate ion : components: : : . .C. :O. :O. :O. + 2e. . . . 24 valence electrons Assemble in accord with the Octet Rule: Practice Draw the Lewis structure for H2CO Draw the Lewis structure for HNO QUESTION 3 How many nonbonding pairs of electrons are in NH2OH? 1. One pair of electrons 2. Two pairs of electrons 3. Three pairs of electrons 4. Four pairs of electrons Exceptions to the Octet Rule The basis for the octet rule is the maximum number of electrons that can be accommodated in the second energy level in the 2s and 2p orbitals. Elements in the third and higher periods are not restricted to 8 electrons in the valence level because of available d orbitals. Examples : :Cl P : :: : : Cl: :: phosphorous pentachloride . :P . + 5 :Cl. . :: PCl5 Cl: : :Cl: Cl: ten electrons around P : :F S :F: : :: : :F : sulfur hexafluoride : :: : : . :S. + 6 :F. :: SF6 :F: F: twelve electrons around S F: Electron-Deficient Molecules There are many exceptions to the octet rule among compounds derived from early main group elements in Period 2 (Be and B). The chemical reactivity of these compounds reflects their electron-deficiency. Examples :: :Cl:Be:Cl: or :Cl-Be-Cl: only 4 valence electrons around Be :: or :F -B-F: :F: : :F :B: F: :F: :: + 3 :F . :: :: :: . .B . :: BF3 boron trifluoride :: berylium chloride :: + 2 :Cl. :: .Be. :: BeCl2 only 6 valence electrons around B QUIZ 1.03 QUESTION 4 Which electronic structure below is the correct Lewis structure of H2CO, where the hydrogen atoms are bonded to the carbon atom? H. .. . .. .. . C ..O . H B H. .. .. . ..C ..O. . H C H. ..C:O: . H D :: choices H. .. ..C.. . ..O .. H A Formal Charge The formal charge on an atom is obtained by subtracting the number of valence electrons that "belong" to the atom in its bonded state from the number of valence electrons in the neutral free atom. Assignment of Valence Electrons in the Bonded State (1) Electrons in covalent bonds are shared equally by the two atoms held together by the bond. (2) Nonbonding electrons are assigned completely to the atom where they are located. The total number of valence electrons assigned to an atom in its bonded state is one half the number of electrons in covalent bonds plus all the nonbonding electrons. Examples of Formal Charges atom :: CH4 H H:C:H H valence electrons in: free atom bonded state formal charge valence electrons in: free atom bonded state formal charge H C atom :: NH3 H:N:H H H N Examples of Formal Charges atom :: NH4+ H H:N:H H :: :: :: CO3 2- formal charge valence electrons in: free atom bonded state formal charge H N atom :O: :O: C :O: valence electrons in: free atom bonded state C O O QUESTION 5 How many valence electrons does carbon have? 1. Three valence electrons 2. Four valence electrons 3. Five valence electrons 4. Six valence electrons 5. Seven valence electrons Quiz 1.04 PRACTICE Assign the charge in the cyanide ion, CN-. Draw a correct Lewis structure for the hydrogen sulfite ion, HSO3-. ...
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