Summary Chapter General, Organic, & Biological Chemistry Janice Gorzynski Smith

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1 Summary Chapter General, Organic, & Biological Chemistry Janice Gorzynski Smith

2 Organic Chem Review: Valence Electrons Example: Determine the valence electrons of Selenium (Se): 1. Find Se on the periodic table 2. Focus on just the row (period) Se is in 3. Count the number of electrons in the s and p orbitals (ie, count to Se from the left side of the row) Count the number of elements in the row (period) that lead up to the element (Se). Remember, do NOT count the transition metals, lacthanides, and actinides. 1 2 X X X X X X X X X X Electron Dot Symbols: Represent the valence electrons by drawing them around the element symbol for Selenium. Se

3 Organic Chem Review: Lewis Dot Structures N 3 Step [1] Step [2] Step [3] Arrange the atoms next to each other that you think are bonded together. Place and halogens on the periphery, since they can only form one bond. Count the valence electrons. The sum gives the total number of e that must be used in the Lewis structure. For each atom the number of bonds = 8 valence electrons. Arrange the electrons around the atoms. Place one bond (two e ) between every two atoms. Use all remaining electrons to fill octets with lone pairs, beginning with atoms on the periphery. N Nitrogen has 5 valence electrons, so it will have 8 5 = 3 bonds. ydrogen will have 2-1 = 1 bond. There are 8 total valance electrons N 1 lone pair: 2 3 bonds: 6 Total e- 8 = total valence e-

4 Organic Chem Review: Resonance Structures Resonance structures exist when there are multiple lewis dot structures with different electron arrangements with the same connectivity between atoms. Resonance structures help us understand delocalization (spreading) of charge within a molecule that stabilizes the anion or cation. Negative charge not localized on 2 of 3 oxygen, but instead delocalized and spread over entire molecule. Other Examples: CO 3 2- and O 3 NO YES

5 Molecule Shape Review: Bond Angle

6 Molecule Shape Lewis Dot Structures Drawing Molecules.. Structural Formula or Complete Structure C C C C Structural Formula or Complete Structure with Geometry Indicated Condensed Structure Skeletal Structure C C C C C 3 C 2 C 2 =C 2

7 !"#$%&'#()* +,'"-*.'/-'"#0* 1,23&456"33&4* 74(/-)2* 891:.*;(/2* <.'//'#*;(/2=*!"#$ C C %&'%()$ "%()$ Carbon- carbon *# + *# + $ single bonds ),-%()$ * * $ %&')()$ ")()$ Carbon- carbon #. */*#. double ),-)()$0),-1&)()2$ bond * * %&'1()$ "1()$ Carbon- carbon #* *#$ triple ),-1()$0%3),1&)()2$ bond $!"4$ -%&5%&'%()$ -%&5"$ Carbon- halide *# + *&$ bond 3-&5657),-%()$!"8#$ %&35-5&$!";#. $ %7<()$!"8"!$ ),-)6$ 8 "5&$ :1"2$ "%7<()$ 0%7<(5"2$ ),-)6$ 0%&'5:1"2$ * %&9)-19)$ "%&$ $! #$ $ Carbon- oxygen- hydrogen *# + 8#$ 7),-%(5&$ bond ),-1&%7<()$ *# Carbon- Nitrogen + *#. ;#. $ bond %7<(5),-%()$ Oxygen *# + 8*# bonded +$ to 29<7),-1&$),-)6$ carbons Carbon- hydrogen 8 single ),-%(%&$ bond & double $*# + *# bond $ to oxygen $ 0%3),%&9)19)2$ 8 * '),5()$ "5()$!! $ 8 $! * $! *! * #$ $ 3%6>5:1&<3$%3<9$ "5<3$%3<9$ 8! $ )?,)6$ "5%,)$ ;#. $ $ %7<9)$ "%7<9)$ Carbon 8 bonded to 2 carbons =65=%(5()$ & $*# double + **# bond + $ $ to oxygen 0%3),5()2$ Carbon 8 bonded an alcohol ),-%(5<3$%3<9$ group & $*# double + *8# bonded $ $ to oxygen 0%3),<3$%3<92$ Carbon 8 bonded to 7),-1&$),-%(5%,)$ an ether group & $*# double + *8*# bond + $ $ to oxygen 07),-1&$%3),%,)2$ Carbon 8 bonded to an ),-%(%7<9)$ amine group & $*# double + *;# bond. $ $ to oxygen 0%3),%7<9)2$ R-S thiols -thiol Carbon bonded to a sulfur atom aromatics benzene Alternating carbon single & double bonds

8 Properties of Organics Polarity 1. Assess the relative electronegativity of atoms bonded together, if there is a difference it is a polar bond. 2. Indicate polar bonds with δ+ / δ - or 3. If polarity of bonds does not cancel draw the overall dipole moment of the molecule using Electron density is disproportionately distributed over the molecule. Above red indicates partial negative charge, or greater electron density, and blue indicates partial positive charge. Effectively oxygen is hogging the electrons

9 Properties of Organics Solubility London Dispersion Forces Dipole-Dipole Forces ydrogen Bonds Weakest Strongest LIKE DISSOLVES LIKE polar molecules dissolve in polar solvents nonpolar molecules dissolve in nonpolar solvents

10 ISOMERS Stereoisomers Spatial Isomers Different spajal arrangement of atoms but with the same connecjvity Same chemical formula Constitutional Isomers Structural Isomers Different connecjvity between atoms Enantiomers Mirror images of a chiral molecule that are not superimposable Diastereomers All stereoisomers that are not mirror images of one another R Cis/Trans Isomers Conformational Isomers RotaJon around C- C single bonds R R R

11 Alkanes Longest Carbon Chain 6 7 R R R C R C R R C R R C R R Smith. General Organic & Biolocial Chemistry 2nd Ed. 11

12 Nomenclature 1 prefix + parent + prefix parent suffix 2 3 suffix What, where are the subsjtuents? Example: 2,4- dimethyl Alkanes ow many carbons in longest chain? Example: hex What is the funcjonal group? Example: ane 2,4- dimethylhexane # Carbons # Greek Root Straight Chain Alkane Name 1 meth methane 2 eth ethane 3 prop propane 4 but butane 5 pent pentane 6 hex hexane 7 hept heptane 8 oct octane 9 non nonane 10 dec decane Alkyl Group Name Structure 1 C3- methyl 2 C3C2- ethyl 3 C3C2C2- propyl 4 C3C2C2C2- butyl 5 C3C2C2C2C2- pentyl 6 C3C2C2C2C2C2- hexyl Smith. General Organic & Biolocial Chemistry 2nd Ed. 12

13 Nomenclature prefix + cyclo- + parent + prefix parent suffix suffix What, where are the subsjtuents? Example: 2,4- dimethyl ow many carbons in the ring? Example: hex What is the funcjonal group? Example: ane 1,3- dimethylcyclohexane 1 2 Cycloalkanes # Carbons # Greek Root Straight Chain Alkane Name 1 meth methane 2 eth ethane 3 prop propane 4 but butane 5 pent pentane 6 hex hexane 7 hept heptane 8 oct octane 9 non nonane 10 dec decane Alkyl Group Name Structure 1 C3- methyl 2 C3C2- ethyl 3 C3C2C2- propyl 4 C3C2C2C2- butyl 5 C3C2C2C2C2- pentyl 6 C3C2C2C2C2C2- hexyl Smith. General Organic & Biolocial Chemistry 2nd Ed. 13

14 Alkanes CombusJon Complete CombusJon heat + C 4 + 2O 2 à CO O Incomplete CombusJon heat + 2C 4 + 3O 2 à 2CO O Smith. General Organic & Biolocial Chemistry 2nd Ed. 14