VIII Weak bonds break in preference to strong bonds and bonds that break to form more stable fragments break Organic Chemistry Final Notes A Mass Spectrometry I Used to identify molecules by weight II Uses a ionized sample III It only record positively charged fragments IV Uses a mass spectrum which plots relative abundance against m z V m z is basicity mass because z 1 VI the base peak is the fragment in the greatest abundance VII Molecular ion M gives the molecular mass of the compound in preference to those that form less stable fragments IX Alpha cleavage happens when the positive charge is shared by two atms X To Find Molecular Formula 1 Take m z value and divide by 13 gives you of carbon 2 H C left over 3 If compound has O then 1 C and 4 H must by subtracted XI McLafferty Rearrangement B IR spectroscopy I From stretching and bending of bonds II 4000 1400 cm 1 functional group region 1 Where the functional groups appear III 1400 600 cm 1 fingerprint region 1 Characteristics of compound as a whole IV Important numbers 1 The bond between the alpha and beta carbon brakes and gamma hydrogen migrates to the oxygen Benzene ring 1600 and O H carboxylic acid CN triple 2260 2200 CC triple 2260 2100 C C 1680 1600 C N 1650 1550 1500 1430 C 0 1780 1650 C O 1250 1050 Alcohol 1050 Ether 1050 Carboxylic acid 1250 V The greater the change in the dipole moment the more intense the absorption VI The more polar the bone the more intense the absorption VII Lighter atoms show absorption band at larger wavenumbers VIII Stronger bonds show absorption bands at larger wavenumbers Ester 1250 and 1050 C N 1230 1020 O H 3650 3200 3300 2500 N H 3500 3300 C H 3300 2700 sp 3300 sp2 3100 sp3 2900 1 IX Because of hydrogen bonding O H and N H bands are lower in concentrated solutions than in dilute solutions Organic Chemistry Final Notes C NMR Spectroscopy I H NMR 1 Each set of chemically equivalent protons produce an NMR signal 2 Reference compound is added and is the base line for chemical shifts 3 Chemical shift Formula 4 Electron withdrawal causes NMR signal to appear at higher frequencies at larger values 5 Protons in electron poor environments show signals at high frequencies 6 Approximate Chemical Shifts CH3 0 85 CH2 1 20 CH 1 55 C C CH3 1 7 Ketone CH3 2 1 Benzene CH3 2 3 CCH triple 2 4 R O CH3 3 3 2R C CH2 4 7 2R C CH R 5 3 I C H 2 5 4 Br C H 2 5 4 Cl C H 3 4 F C H 4 4 5 R NH2 1 5 4 R OH 2 5 Phenol 4 7 Benzene 6 5 8 Aldehyde 9 10 Carboxylic Acid 10 12 Ketone NH2 5 8 7 N 1 rule proton producing the signal N is the number of equivalent protons bonded to adjacent carbons that are not equivalent to the Coupled protons spilt each other and have the same coupling constant distance Hz between two adjacent peaks of a split NMR signal Multiplicity the number of peaks in an NMR signal Trans coupling constant is greater than that for cis 8 Diastereotopic hydrogens two hydrogens bonded to a carbon that when replaced in turn with a deuterium result in a pair of diastereomers are not equivalent protons II C NMR 1 Tells how many different kinds of hydrogens a compind has III Sheilding 2 1 phenomenon caused by electron donation to the environment of a proton the electron shield the proton from Organic Chemistry Final Notes the full effect of the applied magnetic field 2 The more shielded the father to the right its signal appears in the NMR spectrum 3 Deshielded nuclei protons sense a larger effective magnetic field so it comes into resonance at a higher 4 Shielded nuclei protons sense a smaller effective magnetic field so come into resonance at a lower frequency frequency D Carboxylic Acid and Derivatives and the RXN I Naming Carboxylic Acids Systemic Name Common Name Methanoic Acid Formic Acid Ethanoic Acid Acetic Acid Propanoic Acid Propionic Acid Butanoic Acid Butyric Acid Pentanoic Acid Valeric Acid Hexanoic Acid Caproic Acid Propenoic Acid Arcylic Acid 1 Acyl Chlorides Cl replaces OH ic acid is replaced by yl chloride Acyl bromide are possible but less common 2 Ester OR group replaced OH ic acid replaced by ate Salts of COOH are named the same way If cation is present it is named first Cyclic Esters are called lactone 3 Amides NH2 NHR or NR2 replaces the OH Replace the acid name with amide oxa designates the oxygen atom with a number b4 to tell its position The substituents bonded to the nitrogen are stated first followed by amide name Each substituent on the nitrogen has a N Cyclic amides are called lactams aza are used like the oxa was above 4 Derivative of Carbonic Acid Carbonic Acid The OH groups can be substituted with other groups II Physical Properties of Carbonyl Compounds 3 1 Boiling Points Organic Chemistry Final Notes Amide carboxylic acid nitrile ester acyl chloride ketone aldehyde III Fatty Things 1 Fatty Acids Carboxylic Acids with long hydrocarbon chains Unbranched Even number of carbons Saturated no double bond Unsaturated double bonds can be cis or trans Polyunsaturated Fatty Acids fatty acid with more than one double bonds 2 Fats and Oils Triglycerides are where each of the three OH groups in glycerol from a ester with fatty acid Ones that are solid or semisolid at rt are fats Fats are mostly from animals Fats mostly are saturated or only one double bond Ones that are liquid are called oils Oils are mostly from plants Oil are unsaturated fatty acids IV Carboxylic Acid and Derivative React 1 Nucleophile addition elimination reaction Forms a tetrahedral intermediate The weaker the base the better it is as a leaving group If Z weaker then Y Y stays and Z leave Z 2 Relative Reactivity As OH replacement groups Cl OR OH NH2 3 Acyl Chlorides RCOCl CH3OH RCOOCH3 HCl RCOCl H2O RCOOH HCl RCOCl 2CH3NH2 RCONHCH3 CH3NH3Cl Follow same mechanism as nucleophile addition elimination reaction of carboxylic acid 4 Esters Hydrolysis rxn RCOOCH3 CH3CH2OH RCOOCH2CH3 CH3OH Transesterfication rxn 4 Organic Chemistry Final Notes RCOOCH3 CH3CH2OH RCOOCH2CH3 CH3OH Interchanges ester R group with alcohol R group Aminolysis Reaction RCOOCH2CH CH3NH2 RCONHCH3 CH3CH2OH Hydrolyze slowly Rate can be be increased by acid or H Hydrolysis with Acid is reverse but with base it is irreversible 5 Carboxylic Acids Fisher esterification RCOOH CH3OH RCOOCH3 H2O 6 Amides Amides are very unreactive compounds Do react with water and alcohols under acidic conditions React with water to form carboxylic acid React with alcohols to form esters RCONH2 H2O HO RCOO NH3 7 Synthesize of Amines Primary Gabriel Alkyl halide into a primary amine
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