General Chemistry II: Chapters 1 through 12 Notes
General Chemistry II: Chapters 1 through 12 Notes CHEM:1080
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Chapter 1 01212015 0 Every measurement is composed of a number and a unit 0 The number is meaningless without the unit Examples 0 Proper aspirin dosage 325 milligrams or pounds 0 A fast time for the 100meter dash 1000 seconds or days A The Metric System 0 Each type of measurement has a base unit in the metric system 0 The pre x of the unit name indicates if the unit is larger or smaller than the base unit B Measuring Length 0 The base unit of length is the meter C Measuring Mass 0 Mass is a measure of the amount of matter in an object 0 Weight is the force that matter feels due to gravity 0 The base unit of mass is the gram D Measuring Volume 0 The base unit of volume is the liter Numbers used in Chemistry are either exact or inexact An exact number results from counting objects or is part of de nition 0 An inexact number results from a measurement or observation and contains some uncertainty 0 Determining the number of Signi cant Figures 0 Signi cant gures are all the digits in a measured number including one estimated digit All nonzero digits are always signi cant A zero counts when it occurs between two nonzero digits OR at the end of a number with a decimal place A zero does not count when it occurs at the beginning of a number OR at the end of a number that does not have a decimal Rules for Multiplications and Division 0 The answer has the same number of signi cant gures as the original number with the fewest signi cant gures 0 Rules for Addition and Subtraction o The answer has the same number of decimal places as the original number with the fewest decimal places 0 For representation of large and small numbers that have many zeroes at the beginning or the end 0 A Elements and the Periodic Table 0 Pure substance that cannot be broken down by chemical reactions into simpler substances 0 Learn to identify element by its symbol and classify it as metal conduct heat and electricity ductile and malleable non metal poor heat and electrical conductivity or metalloid intermediate properties between metals and nonmetals B Compounds 0 Compound a pure substance formed by chemically combining two or more elements together 0 A chemical formula consists of Element symbols to show the identity of the elements forming a compound Subscripts to show the ratio of atoms in the compound 0 Pure substances formed by combining two or more elements together 0 Compounds are represented by formulas that can be drawn by many ways 0 Different elements are represented by different colors in space lling models 0 Seven elements exist in diatomic state H2 02 l2 0 All matter is composed of the same basic building blocks called atoms Atoms are composed of three subatomic particles Proton 1 Neutron 0 Electron 1 o 1 amu 1661 x 10quot24g Masses of protons and neutrons are rounded to 1 amu Opposite charges attract while like charges repel each other Protons and electrons attract each other but two electrons or two protons repel each other 0 Atomic number is the number of protons in the nucleus Every atom of an element has the same number of protons in the nucleus 0 Different elements have different atomic numbers 0 Z number of protons number of electrons Periodic table is arranged in order of increasing atomic number not mass number 0 Atomic Number and Mass Number 0 Mass number A the number of protons Z the number of neutrons 0 Elements in the Periodic system are arranged according to atomic number Atoms of the same element have the same number of protons but the number of neutrons can vary 0 Isotopes are atoms of the same elements having different number of neutrons o The atomic weight is the weighted average of the masses of the naturally occurring isotopes of a particular element reported in atomic mass units B1 Characteristics of Groups 1A and 2A 0 Elements that comprise a particular group have similar chemical properties 0 Group Number Group Name Properties of Both Groups 0 1A Alkali metals soft and shiny metals 0 2A Alkaline earth elements low melting points good conductors of 0 heat and electricity 0 react with water to 0 form basic solutions B2 Characteristics of Groups 7A and 8A 0 Group Number Group Name Properties of Both Groups 0 7A Halogen exist as two atoms joined 0 together 0 very reactive 0 8A Noble gases very stable 0 rarely combine with any 0 other elements 0 The Unusual Nature of Carbon 0 Carbon s ability to join with itself and other elements gives it a versatility not seen with any other element in the periodic table 0 Elemental forms of carbon include the following carbononly structures diamond graphite buckminsterfullerene 0 Chemical properties of an element are determined by number of electrons in an atom An electron is con ned to a speci c region around the nucleus giving it a particular energy 0 Energy of electron is quantized restricted to certain values Electrons surrounding nucleus are con ned to principal energy levels or shells n1234 etc where 1quot is closest to nucleus shells are divided into subshells s p d and f Subshells consist of orbitals orbital is a region of space where the probability of nding an electron is high and it can hold two electrons Electrons in lower numbered shells are closer to the nucleus and are lower in energy Electrons in higher numbered shells are further from the nucleus and are higher in energy o The chemical properties of an element depend on the number of electrons in the valence shell 0 The valence shell is the outermost shell the highest value of n electrons occupying this shell are called valence electrons Example Be lsquot2 25quot2 o valence shell n2 0 of valence electrons 2 Dots representing valence electrons are placed on the four sides of an element symbol 0 Each dot represents one valence electrons o For 1 to 4 valence electrons single dots are used 0 With gt4 valence electrons the dots are paired Element H C 0 Cl 0 of valence electrons 1 4 6 7 Bonding is the joining of two atoms in a stable arrangement 0 Elements will gain lose or share electrons to reach the electron con guration of the noble gas closest to them in the periodic table 0 There are two different kinds of bonding o lonic bonds result from the transfer of electrons from one element to another 0 Covalent bonds result from the sharing of electrons between two atoms lonic bonds form between a metal and a nonmental Introduction to Covalent Bonding o Covalent bonds result from the sharing of electrons between two atoms and are formed when two nonmetals combine or when a metalloid bonds to a nonmetal 0 Molecule is a compound containing two or more atoms joined together with covalent bonds 0 Lewis structures are electrondot structures for molecules They show the location of all valence e 0 Solid line represents twoelectron bond Covalent Bonding and the Periodic Table 0 Number of bonds for atoms with 1 2 or 3 electrons is 1 2 or 3 0 Predicted number of bonds 8 number of valence electrons 0 Number of bonds Number of lone pairs 4 o How to Draw a Lewis Structure 0 Three general rules Step 1 Draw only valence electrons Step 2 Give every main group element except H an octet of e Step 3 Give each hydrogen 2e Step 4 Use multiple bonds to ll octets when needed a One lone pair of 3 can be converted into one bonding pair of e for each 2e needed to complete an octet n A double bond contains four electrons in two 2e bonds n A triple bond contains six electrons in three 2e bonds For CH3CI Lewis structure is 4 bonds x 2e 8e 3 lone pairs x 2e 6e 14e If all valence electrons are used and an atom still does not have an octet proceed to Step 4 Example Draw the Lewis Structure for C2H4 Step 1 Arrange the atoms H C C H H H Step 2 Count the valence e n 2C x 4e 8e n 4H x 1e 4e n 12e total Step 3 Add the bonds and lone pairs n 5 bonds x 2e 10e n 2 unpaired e 2e n 12 e nAll valence e have been used Step 4 The unpaired es are forming a double bond UHCCH n l l n H H UEach C now has an octet 0 When drawing Lewis structures for polyatomic ions Add one e for each negative charge Subtract one e for each positive charge Example CN U1C X 4e 4e U1N x 5e 5e n 1 charge 1e n10e total Elements in the third row have empty d orbitals available to accept electrons Thus elements such and P and S may have 8 or more than 8e around them 0 Drawing Resonance Structures 0 Resonance structures are two Lewis structures having the same arrangement of atoms but a different arrangement of electrons oUse the VSEPR theory to determine the shape 0 VSEPR Valence shell electron pair repulsion Valence electron pairs surrounding an atoms tend to repel each other and will therefore adopt an arrangement that minimizes this repulsion thus determining the molecule s geometry oTwo groups around an Atom LINEAR Any atom surrounded by only two groups is linear and has a bond angle of 180 degrees UExample is C02 0 Three Groups Around an Atom Any atom surrounded by three groups is trigonal planar and has bond angles of 120 degrees UExample is H2CO 0 Four Groups Around an Atom Any atom surrounded by four groups is tetrahedral and has bond angles of 1095 degrees UExample is CH4 If the four groups around the atom include one lone pair the geometry is a trigonal pyramid with bond angles of 1095 degree UExample is NH3 If the four groups around the atom include two lone pairs the geometry is bent and the bond angle is 105 degrees UExample is H20 Electronegativity is a measure of an atom s attraction for e in a bond 0 Increasing electronegativity to the left and up 0 Pure nonpolar covalent bond electrons shared equally 00 l 04 0 Polar covalent bond electrons shared unequally 04 l 20 lonic bond electron transferred 20 l 40 0 One polar bond is a polar molecule 0 Three polar bonds All dipoles cancel No net dipole Nonpolar molecule 0 Three polar bonds All dipoles reinforce Polar molecule 0 Two polar bonds two dipoles reinforce Polar molecule 0 General Features of Physical and Chemical Changes 0 Physical changes after physical state of a substance without changing its composition 0 Chemical reactions involve breaking bonds in starting materials reactants and forming new bonds in the products 0 Writing Chemical Equations 0 Visible changes might accompany chemical reactions color changes gas evolution solid dissolution or precipitation Heat evolution physical change might occur too 0 Symbol Meaning 0 Reaction Arrow 0 triangle Heat 0 5 solid 0 l liquid 0 9 gas 0 aq Aqueous solution o A mole is a quantity that contains 602 x 10quot23 items 0 This number is Avogadro s number 0 Conversion factors to relate the number of moles of a substance to the number of atoms or molecules 0 602 x 10quot23 atoms or molecules1 mol 0 1 moi602 x 10quot23 atoms or molecules 0 Conversion factors to relate the number of moles of a substance to the weight 0 1802 g H201 mol 0 1 moi1802 g H20 0 How many molecules are contained in 5 moles of C02 0 5 mol x 602 x 10quot23 atoms or molecules1 mol 301 x 10quot23 molecules o The law of conservation of mass dictates that the quantity of each element does not change in a chemical reaction 0 Thus each side of the chemical equation must represent the same quantity of any particular element 0 The charge is conserved in a chemical reaction either Therefore the same charge must be present on both sides of the balance equann Oxidation is the loss of electrons from an atom Reduction is the gain of electrons by an atom Energy is a capacity to do work 0 Chemical bonds is a form of potential energy 0 For a reaction to occur two molecules must collide with enough kinetic energy to break bonds 0 The two molecules must also have the correct orientation 0 For this chart the products have lower energy than reactants triangle H enthalpy of reaction is lt0 so the energy will be released 0 An exothermic reaction is a chemical reaction that releases energy by light or heat It is the opposite of an endothermic reaction Ea the energy of activation is o The difference in energy between the reactants and the transition state 0 Minimum amount of energy needed for reaction to occur 0 The rate of a reaction Kobs is inversely proportional to Ea Larger Ea lower rate Smaller Ea faster rate Slower reactions have a higher hill to climbquot o How Concentration and Temperature Affect Reaction Rate 0 Increasing the concentration of the reactants Increases the number of collisions Increases the reaction rate 0 Increasing the temperature of the reaction Increases the kinetic energy of the molecules Increases the reaction rate Catalysts o A catalyst is a substance that speeds up the rate of a reaction 0 A catalyst is recovered unchanged in a reaction 0 Catalysts accelerate a reaction by lowering Ea Uncatalyzed reaction higher Ea l slower reaction Catalyzed reaction lower Ea l faster reaction 0 Focus on the Human Body Biological Catalysts o Enzymes usually protein molecules are biological catalysts held together in a very speci c 3D shape 0 The active site binds a reactant which then undergoes a very speci c reaction with an enhanced rate 0 People who lack adequate amounts of lactase This enzyme converts the carbohydrate lactose into the two sugars glucose and galactose cannot digest lactose when it is ingested The BronstedLowry de nition is more widely used 0 A BronstedLowry acid is a proton H donor 0 A BronstedLowry base is a proton H acceptor HCI H20 l H30 Cl HCI is a BronstedLowry acid because it donates a proton to the solvent water H20 is a BronstedLowry base because it accepts a proton from HCI BronstedLowry Acids o BronstedLowry acid is a substance molecule or ion that acts as proton donor Therefore it must contain at least one acidic hydrogen atom HCI H2504 HBr HN03 BronstedLowry Bases o A BronstedLowry base is a proton acceptor and must contain a lone pair of electrons that can be used to form a new bond to the proton NaOH KOH MgOH2 CaOH2 o The net charge must be the same on both sides of the equation Amphoteric compound A compound that contains both a hydrogen atom and a loner pair of e it can be either an acid or a base 0 H20 Relating Acid and Base Strength 0 A strong acid HCI is completely dissociated into H30 and CI 0 A weak acid CH3COOH contains mostly undissociated acid 0 A strong base NaOH is completely dissociated into Na and OH 0 A weak base contains mostly undissociated base NH3 0 For the reaction where acid HA dissolves in water 0 HA H20 ll H30 A o The following equilibrium constant can be written 0 K H30A o HAH20 o Ka acid dissociation constant KH20 H30A HA I0 0 Water molecules can react together in an acidbase reaction 0 K H30OH o H20quot2 0 KW ionproduct constant KH20quot2 H30OH Kw is a constant 10 x 10quot14 for all aqueous solutions at 25 degrees C Kw H30OH 0 Neutral H30 OH 0 Acidic H30 gt OH 0 Basic H30 lt OH pH ogH30 The lower the pH the higher the concentration of hydronium ions H30 o Acidic solution pH lt 7 l H30 gt 1 x 10quot7 0 Neutral solution pH 7 l H30 1 x 10quot7 0 Basic solution pH gt7 l H30 lt 1 x 10quot7 Calculating pH from H30 o If H30 12 x 10quot5 M for a solution what is its pH pH ogH30 pH og12 x 10quot5 pH 492 Calculating H30 from pH 0 If H30 pH 492 what is for H30 for the solution H30 10quotpH H30 10quot492 H30 12 x 10quot5 Vaginal pH is normally acidic a pH above 70 can indicate that the amniotic sac has ruptured Elevate pH can also be associated with bacterial vaginosis Fecal pH test is used for diagnosing intestinal infections or other digestive problems In civil engineering to determine the carbonatation spread in concrete structures A buffer is a solution whose pH changes very little when acid or base is added If an acid is added then the excess acid reacts with the conjugate base so the overall pH does not change much Calculating pH of a buffer 0 1 Acid dissociation constant Ka for general acid HA Ka H30A HA 0 2 Rearranging the expression to solve for H30 H30 Ka xl l A o 3 Calculate logH30 0 Organic chemistry is the study of compounds whose molecular backbone is mostly carbon Products such as pharmaceutical drugsmedicine clothes foods gasoline refrigerants and soaps are composed almost solely of organic compounds Some organic products can be obtained directly from natural sources cotton wool and silk as well as vitamins and various drugs Others can be synthetically produced polymers nylon polyethylene polyester arti cial sweeteners synthetic drugs 0 Some examples of Organic Compounds iHII i 3 lt H l I i Tl T Hl ili h tzf m l l ll E imH 39 a r quot lui a2 1 I H E H HJEH Gar emsFa H H l lil l ll HH maillane ethanol all enm H ll l m mui H U I l 3 E l H H H l H I H l I l l if a r N I H H I FEELEmmi til as l a l H i i if l H l i mi m 51 5 i ll if 1 r l l E h H ii I H H l ti C F E l CW 1 All organic compounds contain carbon atoms and most contain hydrogen atoms 0 Carbon always forms four covalent bonds 0 Hydrogen always forms one covalent bond 0 2 Carbon forms single double and triple bonds to other carbon atoms 0 3 Some compounds have chains of atoms and some compounds have rings 0 4 Organic compounds may also contain elements other than carbon and hydrogen 0 Any atom that is not carbon or hydrogen is called a heteroatom N O F Cl Br and l ect The most common multiple bond between carbon and a heteroatom is a carbonoxygen double bond VSEPR Valence shell electron pair repulsion theory 0 Model predicting the geometry of individual molecules from the number of electron pairs surrounding their central atoms The most stable arrangement keeps the groups at a central atom as far away from each other as possible e H A i Q A fee eeetylene belly enti eliel meeel ee lwe ateme eruecl eleh l3 Ha El l Ef e A a ii i ll I HIEE eleme ereruee eeeh G ethylene To draw a 3D tetrahedron on a page we use 0 A solid line for bonds in the plane 0 A wedge for a bond in front of the plane 0 A dashed line for a bond behind the plane Ftnurrizliaar hr Etnagem 1m F39Q iEEEEu ill39cmi nli39 Ell f39aim liu ulnaEl n able 1 I quot F39 l tlular Shaina r un irtma in Eirga lr Eluu ilpau df Ema unwisel H EMF3quot Hlnl nltya W115i J T ul39 lsjfl Etta fal rtui l lrr r n tin rwa autumn l tr 4 it ran Etcm n la ngl finch l l a t t39 IIEUEHI rigl 1 l t E39Z le r G at nj n l nanDar as ITi f quot1 it a IIIIEiE HIE Eiif l hFII39lii M l IE L1 1 a d l I 1L 5339 39I quot g t 39ri39 trrquotEgquotrr39i39i39llle3n Condensed Structures 0 In a condensed structure the twoelectron bond lines and lone pairs on heteroatoms are generally omitted gasmerit Equ H r r 3 ll H MFA H H I til I I til II l L o Skeletal Structures EEEH has 2 ll e bonded it f I H a HH may EH H LGEW G l l L f l h i i Skeletal structurw When drawing a skeletal structure 0 Assume there is a carbon atom at the junction of any two lines or at the end of any line 0 Assume there are enough hydrogens around each carbon to give it four bonds 0 Draw in all heteroatoms and the hydrogens directly bonded to them 0 A functional group is an atom or group of atoms with characteristic chemical and physical properties 0 A functional group contains a heteroatom a multiple bond or sometimes both R Functional Group 0 R carbon backbone o bonded to 0 Functional group a particular functional group Hydrocarbons E1 iIIEETHIH WL lniuuLJi Ellili illii u u FF F39i l 39jHIllll I lllllmli rm IE39II3IIIIlEIiirE EI timid Tabit Vi E Hy39e39drzEziria39ln r39u Wit 3 rin gtiaiinia G aiirai39m t rrinn7 ti r lrl 39 i 3 ii triiigiiln J i 39uln ui39ai39ai Erz39aiig mane ll l IaEt39l r r Harmanairport m i a I 1 it E r quot i i awntale tamj C r z ai h Min g t t H 77134 r r5 Erin1 i ii i 39lil ii lfll FIE Emulath EDI39I39iiFiEilJI39IEI r 1 i 0 Compounds containing a single bond to a heteroatom iH EIEI J 33TH I IIi39Ei39LumH l Emlq llnil Pug pi 39l39llfgl lil39 I llli l ij iLI mpai iil iull 5I fiatwig attire ll 3quot Ermnpmn39isi gw Enrimining a SerbaimnH ler nt m Singing Eranail Mama iii Cummmmitl C iziiig mi 1 iltumsit Filletllliailui ii E lz39l aivilmiitia rjilli liii i ll Emma i9 7 5 Mhyllhniida are Erl r L f 5 J l3 l39 LIL Hi i EL ai i V a w A I H Mcnllml iii G iiHEM A EV 539 quotquot g 4quot v r ielgf u i reelqirl 39 39 E tl ier H ti ll I2H iii Cami r on LEI it amine tillg HH i HIT TIE lEIIEJIII EH 393 ml hill 0 Compounds Containing a CO Group 0 Carbonyl groups carbonoxygen double bonds are present in several different compounds finun n39l ED 39 394 gun I in muqtln 1quot EM 33 I 5 up DIELID El La iru M F El 391L1P 5 P Ed Tag21mm gural t 151 52quot 5413 L Ll l v ELI r g a 939 u i c 7 i i H i a i u itemm E 7 ill FL 39 l E t t H i u fs r awsgrill Id n 7 I 139 a 71 M w F mu i i M E ELE E E if V D u Ester if 7 u 7 i 7 E L in Ml EH ital a i ii i l j 7 a mils 39HDI Emmi Hi in luau C 7 in 5E I E i M E I a u Intermolecular forces determine physical properties such as melting point boiling point and solubility 0 Van der Walls interactionsPolar interactionsleydrogen bondsonic interactions Polarity o A covalent bond is nonpolar when two atoms of identical or similar electronegativity are bonded o A covalent bond is polar when atoms of different electronegativity are bonded Hydrocarbons contain only nonpolar CC and CH bonds so they are nonpolar molecules If a single bond is polar the molecule is polar because it contains a net dipole If the individual polar bonds dipoles cancel in a molecule the molecule is nonpolar If the individual bond dipoles do not cancel the molecule is polar Example Why is CH2C2 a polar molecule Solubility O Solubility is the property of a solid liquid or gaseous chemical substance called solute to dissolve in a solid liquid or gaseous solvent to form a homogeneous solution of the solute in the solvent The solubility of a substance fundamentally depends on 1 The physical and chemical properties of the solute and solvent 2 Temperature pressure especially for gaseous compounds and the pH of the solution Simpli ed solubility rule of thumb is quotlike dissolves likequot Substances with similar intermolecular forces are most likely to mix and dissolve n Hydrocarbons and other nonpolar organic compounds are insoluble in water but are soluble in organic solvents a Polar organic compounds are water soluble only if they are small and contain a N or O atom that can form hydrogen bonds with water Nonpolar compounds are soluble in nonpolar solvents Octane dissolves in CC4 because both are nonpolar liquids that exhibit only London dispersion forces Most ionic and polar covalent compounds are soluble in water a polar solvent Small neutral molecules with O or N atoms that an hydrogen bond to water are water soluble n Example ethanol molecules can form hydrogen bond with water molecules Vitamins An organic compound is called a vitamin when it cannot be synthesized in suf cient quantities by an organism and must be obtained from the diet 0 O Fatsoluble vitamins have many nonpolar CC and CH bonds and few polar functional groups A watersoluble vitamin dissolves in water and contains polar bonds Vitamin A Retinol is an essential component of the vision receptors in the eyes It also helps to maintain the health of the mucous membranes and the skin Vitamin A is mostly nonpolar molecule making it a fat soluble vitamin Vitamin C Ascorbic acid is important in the formation of collagen the connective tissue of the skin A de ciency in vitamin c causes scurvy a condition of sailors in the 1600s who had no access to fresh fruit while at sea It has many polar bonds and many 0 atoms and OH groups making it a watersoluble vitamin 121 Introduction Alkanes are hydrocarbons having only CC and CH single bonds Acyclic alkanes have the general formula CnH2n2 and are called saturated alkanes because they have the maximum number of H atoms per C atom Cycloalkanes contain C atoms joined in one or more rings have the general formula CnH2n All alkane molecules have names that end in the suf x quotanequot 122 Simple Alkanes Acyclic Alkanes Having Fewer than Five Carbons H CH4 H C H methane I H T i 10950 C H quotH Naif H 19 3D representation ballandstick model H H CHSCH3 H C C H ethane I I CHSCchHS propane 3D representation ballandstick model 0 The four carbons in butane can be a straightchain or branched chain alkane H H H H H C H I I I I It IT H C i Cf C I 3 HH c c C H H H H H IL IL IL butane isebutane CH30H20H20H3 4 0 3 in a raw THE H 3 0 5 with a onecarbon branch Butane and isobutene are isomers of each other Isomers are two different compounds with the same molecular formula Constitutional isomers differ in the way the atoms are connected to each other T T T T H f ID O H H ID O ID H H H H H CHBCH20H CHSOCHS ethanol dimethyl ether Acyclic Alkanes Having Five or More Carbons 0 As the number of C atoms increases the number of possible isomers increases of C s Name Structure 6 hexane CH3CH2CH2CH2CH2CH3 7 heptane CH3CH2CH2CH2CH2CH2CH3 8 octane CH3CH2CH2CH2CH2CH2CH2CH3 9 nonane CH3CH2CH2CH2CH2CH2CH2CH2CH3 o 10 decane CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 Classifying Carbon Atoms o A primary carbon 1 degree C is bonded to one another C o A secondary carbon 2 degree C is bonded to two other C o A tertiary carbon 3 degree C is bonded to three other C o A quaternary carbon 4 degree C is bonded to four other C 0 Bond Rotation and Skeletal Structures for Acyclic Alkanes o Rotation can occur around carboncarbon single bonds 0 The zigzag arrangement of atoms is the most stable because it avoids crowding o The skeletal structures of alkanes follow the same zigzag pattern 123 An Introduction to Nomenclature The IUPAC System of Nomenclature o The International Union of Pure and Applied Chemistry provides a system of naming organic compounds Most drugs have three names a Systematic The IUPAC name 242 methylpropylphenylpropanoic acid a Generic The of cial internationally approved name of the drug ibuprofen a Trade The name assigned by the company that manufactures the drug Advil 124 Alkane Nomenclature The names of alkanes with substituents have three parts 0 The parent name indicates the number of C s in the longest continuous carbon chain 0 The suf x indicates what functional group is present 0 The pre x tells the identity location and number of substituents attached to the carbon chain Naming Substituents 0 Carbon substituents are called alkyl groups 0 To name a alkyl group change the quotanequot ending to the parent alkane to yl OOOOO Copyright Tlhe lMcGrawHill Companies Inc Permission required for reproduction or display Table 122 Some Common Alkyl Groups Number of C s Structure Name 1 CH3 methyl 2 CHSCH2 ethyl 3 CH3CH20H2 propyl 4 CH3CH2CHQCH2 butyl 5 CH3CH2CHQCH2CH2 pentyl 6 CHBCHECHQCHQCHQCHT hexyl Naming an Acyclic Alkane o How to name an Alkane using the IUPAC System Step 1 Find the longest continuous carbon chain and name it with an ane ending Step 2 Number the atoms in the carbon chain to give the rst substituent the lower number Step 3 Name and number the substituents u If two or more substituents are identical use pre xes to indicate how many a of Substituents Pre x n 2 di n 3 tri n 4 tetra Step 4 Combine substituent names and numbers parent suf x n Alphabetize the substituents ignoring pre xes n Precede the name of each substituent by the number that indicates its location Sample Problem n Give the IUPAC name for the following compound CH3 CH3CH2 H D l l l CH3 C CH2CH2 C C CH2CH3 H HCH3 a Step 1 Name the parent chain and use the suf x quotanequot since this molecule is an alkane 8 C s in the longest chain l octane a Step 2 Number the chain to give the rst substituent the lower number a Step 3 Name and number the substituents Methyl at C2 ethyl at C5 methyl at C6 n ANSWER 5ethyI26dimethyoctane 125 Cycloalkanes Simples Cycloalkanes o Cycloalkanes contain carbon atoms arranged in a ring 0 Pre x cyclo Parent Suf x Pre x what and where are the substituents Cyclo a ring is present Parent How many C s are in the ring Suf x What is the functional group Naming Cycloalkanes CH3 CH3 Place CH3 groups at C1 and C3 13dimethylcyclohexane not 15dimethylcyclohexane CHZCHB a CH3 Earlierletter lower number ethyl group at C1 methyl group at C3 1ethyl3methyloyclohexane not 3ethyl1 methylcyclohexane 126 Focus on the Environment 0 Fossil Fuels O 0 Natural gas is composed mostly of methane which burns in the presence of oxygen releasing energy Petroleum is a complex mixture of compounds that must be re ned to separate it into usable fractions Gasoline kerosene and diesel fuel are some of the products of petroleum re nement Other portions are used to make plastics drugs fabrics dyes and pesticides 127 Physical Properties Alkanes contain only nonpolar CC and CH bonds Alkanes exhibit only weak intermolecular forces so they have low melting points and boiling points Smaller alkanes are gases at room temperature whereas larger alkanes are liquids Alkanes are insoluble in water Alkanes are less dense than water meaning that they will oat on the surface of water As the number of carbons in an alkane increases the boiling point increases 128 Focus on the Environment Combustion 0 O O Combustion is an oxidationreduction reaction In the combustion reaction alkanes burn in the presence of 02 gas to form C02 and H20 If there is not enough 02 to react incomplete combustion may occur and carbon monoxide is formed instead of carbon dioxide Carbon monoxide is a poisonous gas that binds to hemoglobin in blood limiting the amount of 02 that can be transported to cells
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