Structural Determination Of Organic Compounds
Structural Determination ofOrganic CompoundsHow do you know your reaction worked?How do you know your final product is what you wanted?Is the molecular formula of the product correct?Are the atoms connected correctly to give you the desiredstructure?Can you identify all the functional groups of your product?How can you answer these questions?
Mass Spectrometry (Chapter 14)Provides the molecular mass of a compoundThe compounds are charged (positive or negative ion) and separatedbased on the m/z (mass/charge) ratioOrganic Spectroscopy:Interaction of Light/Energy with matterUV-vis SpectroscopyPresence or not of a chromophore (double bond containing compound)IR SpectroscopyPresence or not of different functional groupsNMR Spectroscopy- Presence or not of different functional groups- Information on C-C and C-H bonding
Mass Spectrometry(Chapter 14)
Understanding Mass Spectra (Chapter 14) The tallest peak in the mass spectrum is called the base peak. For methane the base peak is also the M peak (molecular ion), although this is usuallynot the case. Though most C atoms have an atomic mass of 12, 1.1% have a mass of 13. Thus, 13CH4 is responsible for the peak at m/z 17. This is called the M 1 peak.
Mass SpectrometryProvides the molecular mass of a compoundThe compounds are charged (positive or negative ion) and separatedbased on the m/z (mass/charge) ratioOrganic Spectroscopy:Interaction of Light/Energy with matterUV-vis SpectroscopyPresence or not of a chromophore (double bond containing compound)IR Spectroscopy (Chapter 12)Presence or not of different functional groupsNMR Spectroscopy (Chapter 13)- Presence or not of different functional groups- Information on C-C and C-H bonding
Electromagnetic Spectrum
Electromagnetic SpectrumNMRRadiowaves1 mm – 10,000 kmUV-VisIRUV: 200 – 400 nm800 – 1050 nm Visible: 400 – 800 nm)
IR Spectroscopy (Chapter 12) Absorption of IR light causes changes in the vibrationalmotions of a molecule.
Absorption of IR Light The different vibrational modes available to a molecule includestretching and bending modes. The vibrational modes of a molecule are quantized, so theyoccur only at specific frequencies which correspond to thefrequency of IR light.
Bond Stretching and Bending When the frequency of IR light matches the frequency of aparticular vibrational mode, the IR light is absorbed, causingthe amplitude of the particular bond stretch or bond bend toincrease.
Characteristics of an IR Spectrum In an IR spectrometer, light passes through a sample. Frequencies that match the vibrational frequencies are absorbed,and the remaining light is transmitted to a detector. An IR spectrum is a plot of the amount of transmitted light versusits wavenumber. Most bonds in organic molecules absorb in the region of 4000 cm 1to 400 cm 1.12
Regions of an IR Spectrum The IR spectrum is divided into two regions: the functionalgroup region (at 1500 cm 1), and the fingerprint region(at 1500 cm 1).Figure 13.913
Four Regions of an IR Spectrum Bonds absorb in four predictable regions of an IR spectrum.14
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IR Spectrum of 2-Butanol The OH group of the alcohol shows a strong absorption at3600-3200 cm 1. The peak at 3000 cm 1 is due to sp3 hybridized C H bonds.16
IR Spectrum of 2-Butanone The C O group in the ketone shows a strong absorption at 1700 cm 1. The peak at 3000 cm-1 is due to sp3 hybridized C H bonds.17
IR Spectrum of Octylamine The N H bonds in the amine give rise to two weak absorptionsat 3300 and 3400 cm 1.18
IR Spectrum of Propanamide The amide exhibits absorptions above 1500 cm 1 for both itsN H and C O groups: N H (two peaks) at 3200 and 3400 cm 1;C O at 1660 cm 1.19
IR Spectrum of Octanenitrile The C N of the nitrile absorbs in the triple bond region at 2250 cm 1.20
OH
C O
NMR Spectroscopy (Chapter 13)
Nuclear Magnetic Resonance Spectroscopy Nuclear magnetic resonance spectroscopy is a powerfulanalytical technique used to characterize organic moleculesby identifying carbon-hydrogen frameworks within molecules. Two common types of NMR spectroscopy are used tocharacterize organic structure: 1H NMR is used to determine the type and number of Hatoms in a molecule; and 13C NMR is used to determine the type of carbon atoms in amolecule. The source of energy in NMR is radio waves which have longwavelengths, and thus low energy and frequency. When low-energy radio waves interact with a molecule, theycan change the nuclear spins of some elements, including 1Hand 13C.24
NMR(Nuclear Magnetic Resonance)Spectroscopy
NMR spectroscopy is applied to small and medium sized (proteins)organic molecules.Most commonly used: 1H NMRAll different hydrogens in a compound have a unique interaction withthe applied magnetic field resulting in different NMR signals.What is the origin of the NMR signal?Same basic technique as:MRI(Magnetic Resonance Image)An MRI is NMR-spectroscopy applied to wholebody parts, not individual molecules(Biological NMR).Human body: 75% waterThe 1H atoms in each water molecule interactdifferently with the applied magnetic fieldbased on their different environments,resulting in different signals.
Magnetic Fields in NMR When a charged particle such as a proton spins on its axis, itcreates a magnetic field, causing the nucleus to act like a tiny barmagnet. Normally, these tiny bar magnets are randomly oriented in space. However, in the presence of a magnetic field (B0), they areoriented with or against this applied field. More nuclei are oriented with the applied field because thisarrangement is lower in energy. The energy difference between these two states is very small ( 0.1cal).27
1HNMR Spectra An NMR spectrum is a plot of the intensity of a peak against itschemical shift, measured in parts per million (ppm).28
Regions in the 1H NMR Spectrum33
13C NMR Spectrum Example13CSpectra are easier to analyze than 1H spectra because thesignals are not split. Each type of carbon atom appears as a single peak.39
NMR spectroscopy is applied to small and medium sized (proteins) organic molecules. Most commonly used: 1H NMR All different hydrogens in a compound have a unique interaction with the applied magnetic field resulting in different NMR signals. What is the origin of the NMR signal? Same basic technique as: An MRI is NMR-spectroscopy applied to whole
General Introduction to Organic Compounds Most of the foodstuffs that we consume every day such as sugar, fats, starch, vinegar, etc are basically organic compounds. Even though the . hydrocarbons and their derivatives is known as organic chemistry. Browse more Topics under Organic Chemistry Classification of Organic Compounds Isomerism
meth-eth-prop-but-pent-6 8 7 9 10 hex-hept-oct-non-dec-5 3.2 Naming Organic Compounds Organic H 3C CH 2 CH 2 CH 3 H 2C CH2 H 2C CH CH 2 3.3 Naming Organic Compounds Organic H 3C CH CH CH2 H3C CH CH3 CH3 CH 3 CH 3 CH 3 3.4 Naming Organic Compounds Organic Name all
All organic compounds contain carbon atoms, but not all carbon-containing compounds are classified as organic. examples: Na 2 CO 3, CO, and CO 2 are considered inorganic. Organic compounds can be defined as covalently bonded compounds containing carbon, excluding carbonates and oxides. Chapter 22
256 Study Guide for An Introduction to Chemistry Section Goals and Introductions Section 15.1 Organic Compounds Goals To describe carbon-based compounds, called organic compounds. To describe the different ways that organic molecules can be represented and show you how to convert from one way to the others. To show how you can recognize different types of organic compounds.
264 Study Guide for An Introduction to Chemistry Section Goals and Introductions Section 17.1 Organic Compounds Goals To describe carbon-based compounds, called organic compounds. To describe the different ways that organic molecules can be represented and show you how to convert from one way to the others. To show how you can recognize different types of organic compounds.
Chapter 11 Introduction to Organic Chemistry: Hydrocarbons Firefighters must be knowledgeable about fire codes, arson, and the . 11.1 Organic Compounds Organic chemistry is the study of carbon compounds. Organic compounds such as vegetable oil contain carbon and hydrogen.
3. Organic Compounds: Alkanes and Cycloalkanes Based on McMurry’s Organic Chemistry, 7th edition, Chapter 3 2 Families of Organic Compounds S tru cal fe sh mk ip ob y compounds by reactivity are call functional groups O rg an ic o mpu d sb etf l yh common structural features C h ap ter3d
1. Organic Spectroscopy–William Kemp 2. Spectroscopy of organic compounds – P.S. Kalsi 3. Spectrometric identification of Organic compounds-Silverstein, Bassler & Morrill 4. Spectrometric identification of Organic compounds-Silverstein & Webster 5. A complete introduction to NMR Spectroscopy-Roger S. Macomber 6. Organic Spectroscopy .
