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The Functional Groups

The Functional Groups. Functional Groups. Most organics include substituents May include oxygen, nitrogen, sulfur and/or phosphorous Known as functional groups because they are the chemically functional part of the molecule capable of chemical reactions Written as:

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The Functional Groups

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  1. The Functional Groups

  2. Functional Groups • Most organics include substituents • May include oxygen, nitrogen, sulfur and/or phosphorous • Known as functional groups because they are the chemically functional part of the molecule capable of chemical reactions • Written as: • R – functional group • R = represents the chain or rings attached to the functional group

  3. Functional Groups We will learn more about: Alcohols Ethers Carboxylic acids Esters When naming these organics the functional group must be part of the parent chain Just like double or triple bonds

  4. Halogen Substituents • Halocarbons – organic compounds with halogen substituents (F, Cl, Br or I) • The halogen is indicated like all other alkyl groups • The addition of halogens = increase of Van der Waals forces = increase boiling point • Example: • 1,2-dibromobenzene • Ortho-dibromobenzene

  5. Alcohols • An organic compound with an OH or hydroxyl group • May be classified based on the number of R groups attached to the carbon with the OH group • Primary Alcohol –one R group attached to the C-OH • Secondary Alcohol – two R groups attached to the C-OH • Tertiary Alcohol – three R groups attached to the C-OH p.730 in text

  6. Naming Alcohols • Drop the ‘e’ from the alkane parent chain name and add an ‘ol’ • The parent chain includes the C attached to the OH • OH is like a double or triple bond • Receives preference when numbering the parent chain • Indicate where the OH group is with a prefix • E.g. 2-butanol • Two or three OH groups are represented as ‘diols’ and ‘triols’ • Example: 1,2-ethandiol

  7. Properties of Alcohols • Higher boiling point – because of intermolecular H-bonds • Alcohols ≤ 4 carbons are soluble in water • Carbon chain = non-polar • Hydroxyl group = polar • Alcohols > 4 carbons • Ratio of non-polar: polar increases • Not soluble in water

  8. Uses for Alcohols Isopropyl alcohol = rubbing alcohol, perfume Ethylene glycol = antifreeze Glycerol = moistening agent in cosmetics, foods & drugs Ethanol = liquor Methyl alcohol = wood alcohol

  9. Ethers • Oxygen bonded to two carbon groups • R-O-R

  10. Naming Ethers • The two groups are named alphabetically and followed by the name ‘ether’ • Example: ethylmethyl ether • Some ethers are symmetric (both R groups are the same) • Named using the prefix ‘di’ • Example: diethyl ether

  11. Uses & Properties of Ethers Diethyl ether – first general anesthetic More soluble than other HCs, but less soluble than alcohols More H-bonds than other HCs, but less than alcohols Higher bp than other HCs and lower bp than alcohols

  12. Carboxylic Acids Carboxylic acid – a compound with a carboxyl group Carboxyl group – consists of a carbonyl and a hydroxyl group Carbonyl: C=O Hydroxyl: OH The general formula is: RCOOH Weak acids  ionize slightly in solution  carboxylate ion & a hydrogen ion

  13. Naming Carboxylic Acids Replace the ‘e’ ending of the parent alkane with ‘oic acid’ Example: Hexanoic acid

  14. Common Names of Carboxylic Acids Many have common names based on a greek or latin origin Ethanoic acid = acetic acid = vinegar Household vinegar = 5% acetic acid Many fatty acids IUPAC names aren’t commonly used

  15. Properties of Carboxylic Acids Low molar mass carboxylic acids= colourless, volatile liquids with sharp, unpleasant odours Higher molar mass carboxylic acids= nonvolatile, waxy, odourless solids with low mp E.g. stearic acid (from beef fat) – used to make cheap wax candles Aromatic carboxylic acids = crystalline solids @ room temp Can form intermolecular H-bonds= higher bp & mp than other HCs of similar size Carboxylic group is polar & readily H-bonds with water Low molar mass carboxylic acids are completely miscible with water Not true of high molar mass acids (non-polar:polar ratio increases)

  16. Esters Have pleasant, fruity odours Give fruits & perfumes their smells Derivatives of carboxylic acids in which the OH has been replaced by a O-R Remember R = carbon chain General formula for an ester is: RCOOR 1 C=O 1 C-O

  17. Naming Esters • You are going to be referring to the two R groups. • The R group double-bonded to the O is the parent chain • Ends in ‘anoate’ • The R group single-bonded to the other O is the alkyl group • Like always ends in ‘yl’

  18. Naming Esters Alkyl groups come first, followed by the parent chain ending in ‘anoate’

  19. Properties of Esters Neutral substances Do not contain any H attached to an electronegative element = cannot form intermolecular H-bonds = held together by weak attractions (Van der Waals) Much lower bp than carboxylic acids Esters with < 5 C somewhat soluble in water Esters with > 5 C limited solublity in water

  20. Esterification Carboxylic acid + primary or secondary alcohol = ester Condensation reaction because water is produced The reaction is reversible Example: Ethanoic acid + methanol = methyl ethanoate+ water

  21. Reversal of Esters When heated in strong acid or base solutions esters begin to break down If water is then added the ester will breakdown into its corresponding carboxylic acid and alcohol Example: ethyl ethanoate

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