OCHEMTABLECHAPTER2.pdf CHEM 121
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This 16 page Study Guide was uploaded by sol on Sunday December 21, 2014. The Study Guide belongs to CHEM 121 at University of the Pacific taught by Dr. Xue in Fall. Since its upload, it has received 262 views. For similar materials see Organic Chemistry in Chemistry at University of the Pacific.
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Date Created: 12/21/14
Hydrocarbons compounds that contain only carbon and hydrogen atoms Alkanes ane don39t have multiple bonds between carbon atoms Alumna E HI 1 133 JIIZ ZlII Il39lEll En E El n burn g a39i391Ja l WH EIII139J39J39i39IJE L EPEEEETZ EquotH53Hg a39El39D39iE rum1 Edmu II T39iE T T 1quot 39r39i139I39LaII1 m hthlnlu MethaneCH4 EthaneCH3 CH3 PropaneCH3 CH2CH3 ButaneCH3 CH2CH2CH3 Alkyl groups R obtained by removing a H atom from an alkane Methyl Ethyl Propyl Isopropyl Butyl Alkyl groups are hydrophobic their hydroxyl group is hydrophillic Haloalkanes compounds in which a halogen atom Fluorine chlorine bromine iodine replaces a H atom of an alkane Generic formula R X Can be primary secondary or tertiary based on the carbon atom to which the Halogen atom is attached Halneail ngasne If2HgElHa l39LiZiEIEHZlE1l39l3l39l EEtl39Iquot lrhlcri e Alkene ene contain at least one CC a double bond a mhm a compound with a halogen atom R i i J bonded to an gE39Ea alkene carbon HEH EIEl HEH ElEIH FEE EllIEFE FEF3 GHQ Ch i1Hamp K mne l tn Aklynes yne contain at least one CC triple bond AI Iawnae EH p t CFI l Ci TH E hyne gtq cnt Aromatic compounds A special type of ring ex Benzene ring Ammmiir JIII 39i 39iZiIZ Iing 1 rH 53 H 3 EIEi39 Efl39lE 391IEi39iE 39il39lIE E1 Phenyl group benzene group attached to some other group of atoms in a molecule Benzyl group Combination of a phenyl group and a methylene group CH2 Benzene all of the CC bonds in benzen are one and onehalf bonds and have bond angles of 120 degrees compound with a halogen atom bonded to an aromatic ring Functional Group Alcohol directly attached Hydroxyl OH group attached to an sp3 hybridized C atom may be viewed as hydroxyl derivatives of alkanes and as alkyl derivatives of Water Classi ed as primary secondary or tertiary alcohols based on the degree of substitution of the C to which the hydroxy group is Only circle the OH and bond llna1su HGH H3IHCII a 1quotiha39rII i lIr39 EIiI1I2lTII2I Phenol When a hydroxyl group is Circle benze ring and the bonded to a benzene ring the combination of the ring and the hydroxyl is called the phenol hydroxyl group F enual H 39 mEq Elf F F H H P Lg 339l39uIIyI 39l ruILl Ethers General formula ROR or RO Naming name the two alkyl R Where R may be an alkyl or groups attached to the oxygen phenyl group diff from R atom in alphabetical order and add the word ether Ethers can be thought of as EEHEF derivatives of Water in which both H atoms have been replaced I I by alkyl groups E n a1 r 3 H 5 i 391IiquotiZiquotJ3Ej39lquot 39iLliquotiZi39IE39l Iii39I39IIiquoti Iilp39 E TI Ii J39 Amines Amines may be considered as organic derivatives of ammonia NH3 can be classified as primary secondary or tertiary based on the number of organic groups that are attached to the nitrogen atom the nitrogen atom of an amine can be considered to be sp3 hybridized with the unshared electron occupying one orbital Naming name in alphabetical order the alkyl groups attached to the N atom using the pre xes di and tri if the groups are the same Amine Funetie el V grreu H H G 31 lFlT39lHg r ener t at fermula HENLH ll3quot39 Sp ci ElH3lNlHE eae11le IEUPFLC l39539i l1l391EIl391El e3me mine Lemme iquotMI e El1rl ma ie amine that is bonded to an oxygen or nitrogen atom The functional group including the carbonyl and hydroxyl is called the carboxyl group COOH or CO2H insert screenshots from page 113 examples include formic acid acetic acid and benzoic acid Eamrbnxylmnz Acid 1 5 HCCZIIH T 393 HEEEH Edwinair p F39uEEic auil Esters Have the general gormula RCO2R39 or RCOOR39 a carbonyl group is bonded to an alkoxyl OR group Ester UH aE39 39ElH hi thyl EI I1aIm1tE 139539iEILl391iF1 ac E Ei1lIE Amides Have the formulas RCONH2 Screenshot pg 1153 RCONHR39 or RCONR39R where a carbonyl group is bonded to a lAmslE2 nitrogen atom bearing H andor alkyl groups H E Il1at1at11i ilnE 1 quotLie1anquotr1i 39lit Nitriles In IUPAC acyclic nitriles are named by adding the suffix nitrile to the name of the correspondng hydrocarbon The carbon atom of the CN group is assigned number 1 Examples Ethanenitrile Butanenitrile Cyclic nitriles are named by adding the suffix carbonitrile to the name of the ring system to which the CN group is attached Example Benzonitrile for C6H5CN Has the formula 2R C triple bond N The C and N of a nitrile are sp hybridized A Nllitr lllea C E 1 HIGH E 391aI1Eni11ilE equot39nz39IuaJr139LI1 iLE PHYSICAL PROPERTIES AND MOLECULAR STRUCTURE Note Liquid at room temperature and 1 atm pressure gt if We know bp of our desired product and the bp of the byproducts and solvents that may be present in the reaction mixture gt We can decide Whether or not simple distillation will be a feasible method for isolating our products if our product is a solid then we must know its melting point and its solubility in diff solvents to isolate the substance by crystallization gt ATTRACTIVE Relative Strength Type ELECTRIC FORCES EX Melting point of a substance is the temp at Which an equilibrium exists between the wellordered crystalline state and the more random liquid state Cationanion Strongest gt high boiling point and even higher melting point Covalent bonds Strong Iondipole moderate Water is highly polar so it solvates ions The energy supplied by the formation of iondipole forces is great enough to overcome both the lattice energy and interionic attractions of the crystal Intermolec ular Forces van der Waals Forces Hydrogen bonds Moderate to Weak Very strong dipole dipole attractions occur between H atoms bonded to small strongly elctronegative atoms 0 N or F and nonbonding electron pairs on other such electronegative atoms Dipole dipole Weak Most organic molecules have a permanent dipole moment resulting from a nonuniform distribution of the bonding electrons Acetone acetaldehyde Dispersion London forces variable Electrons move and temporary dipoles are created 2 Factors determining the mag of disp forces 1The relative polarizability of electrons of the atoms involved electrons of large atoms are easily polarized 2relative surface are of the molecules involved Molecules that are generally longer flatter or cylindrical have a greater surface area available for intermolecular interactions than more spherical molecules and con sequently have greater attractive forces between them than the tangential interactions between branched molecules Factors that affect the melting point is the compactness and rigidity of their indiviual molecules Symmetrical molecules gt Higher melting point Boiling point of a liquid is the temp at which the Vapor pressure of the liquid equals the pressure of atomosphere above it are pressure dependent factors that affect boiling temp Heavier molecules gt greater thermal energy larger surface areas more intermolecular dispersion attraction gt greater thermal energy Tip when trying to figure out order of bps of molecules look at their bonds Solubilities Dissolution of a solid in a liquid The energy required to overcome lattice energies and intermolecular or interionic attractions comes from the formation of new attractive forces between solute and solvent Solubility Rule Like dissolves like We find that for compounds containing one hydrophilic group and thus capable of forming strong hydrogen bonds the followng approximate guidelines hold compounds with one to three carbon atoms are water soluble compounds with four or five carbon atoms are borderline and compounds with six carbon atoms or more are insoluble When a compound contains more than one hydrophilic group these guidelines do not apply Polysaccharides Chapter 22 proteins Chapter 24 and nucleic acids Chapter 25 all contain thousands of carbon atoms and many are water soluble They dissolve in water because they also contain thousands of hydrophilic groups INFRAED SPECTROSCOPY instrumental techique that can give evidence for the presence of various funtional groups IR spectroscopy depends on the interaction of molecules or atoms with electromganetic radiation Infrared radiation causes atoms and groups of atoms of organic compounds to vibrate witih increase amplitude about the covalent bonds that connect them Functional groups of organic molecules include speci c arrangements of bonded atoms so absorption of IR radiation by an organic molecule will occur at speci c frequencies characteristic of the the types of bonds and atoms present in the speci c functional groups of that molecule Vibrations are quantized and as they occur the compounds absorb IR energy in particular regions of the IR portion of the specctrum How does an By passing a beam of IR The position of an absorption band peak in an IR infrared radiation through a sample and spectrum is speci ed in units of Wavenumbers spectrometer comparing the radiation Wavenumbers reciprocal of Wavelength when operate transmitter through the sample Wavelength is expressed cms and theregore give the with that transmitted in the number of Wave cycles per cm absence of the sample The spectrometer plots the results as Larger wavenumber higher frequency of the Wave a graph showing absorbance higher the frequncy of the bond absorption versus frequency or Wavelength What are the stretching vibration 2 atoms Frequency of a given stretching vibration in an veriety of joined by a covalent bond move IR spectrum can be related to 2 factors Ways in back and forth as if joined by a masses of the bonded atoms light atoms vibrate at which a spring higher frequencies than heavier ones molecule can 3 atoms relative stif iess of the bond triple bonds are vibrate symmetric stretching stiffer and vibrate at higher frequencies asymmetric stretching an inplane bending Vibration scissoring an outofplane bending Vibration twisting In order for a vibration to occur with the absorption of IR energy the dipole moment of the molecule must change as the Vibration occurs gt Methane does not absorb IR energy for symmetric streching of the 4 CH bonds asymmetric streching does lead to an IR absorption Symmetrical Vibrations of the CC double and triple bonds of ethene and ethyne do not result in the absorption of IR radiation either How do we interpret IR spectra All hydrocarbons give absorption peaks in the 2800 3300 cm1 region that are associated with carbon hydrogen stretching vibrations The carbon hydrogen stretching peaks of hydrogen atoms attached to 1sp hybridized carbon atoms occur at highest frequencies about 3300 cm alkyne The carbon hydrogen stretching peaks of hydrogen atoms attached to sp2 hybridized carbon atoms occur in the 3000 3100 cm1 region The carbon hydrogen stretching bands of hydrogen atoms attached to sps hybridized carbon atoms occur at lowest frequencies in the 2800 3000 cm1 region Carbon carbon double bonds give absorption peaks in the 1620 1680 cm1 region and carbon carbon triple bonds give absorption peaks between 2100 and 2260 cm1 Absorptions arising from carbon hydrogen bending vibrations of alkenes occur in the 600 1000 cm1 region With the aid of a spectroscopy handbook the exact location of these peaks can often be used as evidence for the substitution pattern of the double bond and its configuration Carbonyl group The carbon oxygen doube bond stretching frequency of carbonyl groups gives a strong peak between 1630 and 1780 cm1 i quoti i i i H int H H H H H H H H UH H UH H HHHE N hy H ili lill E lt f E l ifil 39lliquotllIllquotE IElfl 1 iquot4 iquotquotirquotmil 1 ill lfl I i ElIllf 1 ll illquotl5 ITg V ll 1 ll llT II gS l 1EEI lE3939IfI ll Hydroxyl group The IR absorption of an alcohol or phenol O H group is in the 3200 3550 cm1 range and most often it is broad typical broadness of the peak is due to association of the molecules through H bonding which causes a wider distribution of stretching frequencies for the 0H bond alcohol or phenol present as a very dilute solution in a solvent that can39t cont to H bonding 0H absorption occurs as a very sharp peak in the 35903650 region increasing the concentration of the alcohol or phenol causes the sharp peak to be replaced by a broad band in the 32003550 Carboxylic Acid group Note if both carbonyl and hydroxyl stretching absorptions are present in an IR spectrum there is good evidence for a carboxylic acid functional group although it39s possible that isolate carbonyl and hydroxyl groups could be present in the molecule The hydroxyl absorption of a carboxylic acid is often very broad extending from 3600 cm1 to 2500 cm1 Amines N H Primary 1 and secondary 2 amines give absorptions of moderate strength in the 3300 3500 cm1 region Primary amines exhibit two peaks in this region due to symmetric and asymmetric stretching of the two N H bonds Secondary amines exhibit a single peak Tertiary amines show no N H absorption because they have no such bond A basic pH is evidence for any class of amine Note Hydrogen bonding causes N H stretching peaks of 1 and 2 amines to broaden The NH groups of amides give similar absorption peaks and include a carbonyl absorption as well How to interpret an IR spectrum without any knowledge of the structure an IR spectrum can often point toward the presence of certain functional groups if one pays particular attention to signals whose peak positions are distinct from other groups and is consistently strong enough to be observed The latter is an important consideration as there can be variations in signal strength for certain groups dependent on what other groups are in the molecule and some signals overlap with others making a de nitive assignment impossible Here are some examples of what one might consider in a firstpass assessment of any IR spectrum to generate what are likely to be correct answers about some of the functional groups that are present Only CO stretches tend to have a tight strong absorbance in the 16301780 cml range We may not be able to identify what kind of carbonyl group is present but we can tell that there is at least one carbonyl group Only the stretches of nitrile or alkyne bonds tend to appear between 2000 and 2300 cml so these can be fairly readily assigned Only hydroxyl groups as in alcohols or carboxylic acids tend to create a large and broad signal at about 3300 cml these groups are easy to identify assuming the sample is not contaminated with water Only amines tend to produce broad but smaller peaks than hydroxyl peaks around 3300 cml The number of those peaks can sometimes tell if there is one or two hydrogens attached to that nitrogen atom ISOMERS
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