CHEM 2211 Exam 1 Study Guide Lectures 18 Lecture 1 14 August 2013 I II Molecular Orbital Theory A Molecular Orbitals can either constructively overlap or a destructively overlap B Constructive overlap results in a bond Destructive overlap results in a nodal space and Antibonding Linear Conservation of Atomic Orbitals A The number of atomic orbitals consumed equals the number of molecular orbitals produced B Sigma star and pi star are Antibonding orbitals that allow atoms to break bonds with each other C Molecules of equal electronegativity each contribute an atom to the bond D Atoms of different electronegativity unequally contribute electrons to the bond meaning that the more electronegative atom is more similar to the sigma bond than to the sigma star bond Conversely the least electronegative atom is more similar to the sigma star bond than to the sigma bond Lecture 2 16 August 2013 I II Br nsted Lowry Acid Base Theory A Bases are proton acceptors and form OH ions Acids are proton donors and form anions Ka value A Ka is the likelihood a chemical will lose a proton The higher the K a value the higher the likelihood the chemical will lose its proton and the stronger the acid B Since Ka is a very small number the pKa is used instead The formula for pKa is H3O A p K a log III C The lower the pKa the stronger the acid Factors that effect pKa IV V VI A Type of bond i Because hydrogen bonds are a stronger attraction between molecules molecules with them are harder to depronate and have a higher pK a value B Size i Poor orbital overlap cause molecules of missed matched size to be easier to depronate than molecules of similar size C Electronegativity i The more electronegative an atom or molecule is the less likely it is to depronate Conjugate Acids and Bases A Every base has a conjugate acid and every acid has a conjugate base To determine the equilibrium of a system the side with the highest pK a is where the equilibrium will shift Resonance Structures A A resonance structure is the average of two or more structures which differ only in the placement of electrons Resonance structures are more stable because the electrons are shared across the molecule and make the molecule less reactive IUPAC nomenclature A Created a standardized way of naming organic molecules B Each name has a standard prefix for the number of carbons and a suffix that specifies the type of molecule KNOW the first thirteen prefixes i ii iii iv v vi vii viii VII VIII MethEthPropButPentHexHept ix x xi xii xiii xiv OctNonDecUndecDodecTridec Line angle structures aka Skeleton structures A Remember that lines are bonds angles are points and hydrogens are implicit Functional groups and other atoms are completely drawn in meaning their hydrogens are included Alkanes A Suffix ane B All single bonded carbons symmetrical nonpolar have London dispersion forces Lecture 3 19 August 2013 I II An Alkyl Group is when a hydrogen is removed from an alkane A Can have different functional groups attached B The carbons can be primary secondary or tertiary C For the common naming system an alkyl group with three carbons can be either propyl or isopropyl group i A propyl group is a carbon bonded to one other carbon ii An isopropyl group has a secondary carbon bonded to two CH3 groups D For the common naming system a four carbon alkyl substituent can be either butyl isobutyl sec butyl or tert butyl i The rules for butyl and isobutyl are the same as for propyl and isopropyl ii Sec butyl is when a hydrogen is removed from a secondary carbon iii Tert butyl is when a hydrogen is removed from a tertiary carbon IUPAC naming of Alkanes A Determine the longest parent chain B Number the chain in the direction that gives the substituent s the lowest number possible C When more than one substituent exists the chain is numbered in the direction that yields the lowest number and the substituents are named in alphabetical order D Prefix di tri tetra etc indicate the number of identical substituents on the parent chain E If numbering both way yields the same number for different substituents then the first named group gets the lowest number F In a highly branched compound where the substituent also has branched portions the substituent s name is in parenthesis and is accompanied by a number indicating a position on the substituent G In the case that two hydrocarbon chains have the number of carbons choose the one with the most substituents Lecture 4 21 August 2013 I Cycloalkanes A Alkanes that form a ring and have two less hydrogens than the straight chain alkanes B Naming i Cycloalkanes are considered the parent chain unless a straight chain substituent has more carbons then the straight chain is the parent chain 1 If only one substituent exists then no numbers are needed to identify its place on the cycloalkane ii If two substituents are present on the ring then the first one alphabetically is denoted as number one iii When a cycloalkane has more than one substituent then the first substituent is the substituent that yields the lowest number for the second substituent II Alcohols A Formed when OH attaches to an alkyl group and can be primary secondary or tertiary depending on the carbon they re attached to B Naming i First drop the e at the end of the alkane name and add ol ii The parent chain is the longest chain with the OH attached iii OH group has the lowest possible number when numbered on the parent chain iv The suffixes diol triol etc is added to compounds with more than one OH attached v When both the functional group and the substituent are present and or have the same number when numbered both ways then the functional group gets the lowest number vi Multiple substituents on an alcohol are listed alphabetically Lecture 5 23 August 2013 I II III Alkyl Halides A Can be primary secondary or tertiary B The common name is Alkyl Group Name Halide ide suffix C IUPAC nomenclature states that the halide is named first and the alkane group second Ethers A One oxygen bonded to two alky groups B Common name is to add names of two alkyl groups followed by ether C IUPAC way is to drop the yl and add the suffix oxy and then the alkane name i Shortest substituent gets the oxy suffix Amines A Deemed primary secondary tertiary or quaternary by the number of group it is bonded to B Common Naming states that the alkyl groups be named in alphabetical order and amine added to the end C IUPAC naming states that the e be replaced by amine and any group bonded to