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Organic Chemistry Reviews Chapter 2. Cindy Boulton September 7, 2008. Functional Groups. Functional Group Certain characteristics of a particular arrangement of atoms to determine how a molecule reacts Alkenes Hydrocarbon with at least one double bond Alkynes
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Organic Chemistry ReviewsChapter 2 Cindy Boulton September 7, 2008
Functional Groups • Functional Group • Certain characteristics of a particular arrangement of atoms to determine how a molecule reacts • Alkenes • Hydrocarbon with at least one double bond • Alkynes • Hydrocarbon with at least one triple bond • Alkanes do not have a functional group
Functional Groups cont. • Alcohols • A hydroxyl group (-OH) attached to an sp3 hybridized carbon • Ex: methyl alcohol or methanol • Carboxylic Acids • A carbonyl group (C=O) bonded to a hydroxyl group (-OH) • Ex: Formic Acid • Phenyl Group • A benzene ring is attached to another atom in a molecule • One Hydrogen removed to attach benzene ring to carbon chain
Functional Groups cont. • Halogen • A halogen atom (-X, X=F, Cl, Br, or I) replaces a hydrogen atom on an alkane • Alkyl Halide: carbon-halide • Ex: methyl iodine, ethyl flouride
Classifying sp3 Carbons • Number of carbons directly attached to a specific carbon • Primary (1o ) – one carbon attached • Secondary (2o ) – two carbons attached • Tertiary (3o ) – three carbons attached • Quaternary (4o ) – four carbons attached • Example: Propyl Bromide
Infrared (IR) Spectroscopy • Identify functional groups • Light source • Wavelength below red • Monochrometer • Select wavelength of light source • Dial to select a range of wavelengths over time • Sample • Absorb light • Detector • Identifies new wavelength • Read out device • Peaks tell which functional groups in the sample
The Spectrum • X-axis: Light wavelength (cm-1 ) from 4000-600 • Y-axis: Percent Transmission (% T) from 0-100 • How much of the wavelength got through • Baseline at 100% for when no functional group detected at wavelength • Fingerprint Region • 1400-600 • Specific for each molecule
The Spectrum cont. • Alkane Spectrum • Long, jagged peak below 3000 for C-H bonds • Alcohol Spectrum • Big, broad peak at 3300 for –OH • Long, jagged peak below 3000 for C-H bonds • Carboxylic Acid Spectrum • Big, broad, and jagged peak from 3300-3000 for combined C-H bond and for –OH • Long, sharp peak at 1700 for C=O