Finals Orgchem LEC

• Aldehyde


  Functional group is a carbonyl group bonded to a hydrogen atom
• Methanal (formaldehyde)


  Simplest aldehyde, carbonyl group bonded to 2 hydrogens
• Other aldehydes


  Carbonyl group bonded to 1 hydrogen and 1 carbon group
• Ketone


  Functional group is a carbonyl group bonded to 2 carbon groups
• a-carbon

  Carbon atom adjacent to a carbonyl group
• a-hydrogen

  Hydrogen atom bonded to the α-carbon
• Unsaturated aldehydes


  Indicate presence of carbon-carbon double bond by changing ending of parent alkane from -ane to -enal
• Numbering carbon chain for unsaturated aldehydes

  1. Begin with aldehyde carbonyl carbon

  2. Show location of carbon-carbon double bond by number of its first carbon
• IUPAC name for aldehydes

  Change suffix -e of parent alkane to -al
• No need to use number to locate aldehyde group as it can only be at end of parent chain
• IUPAC name for ketones


  • Parent alkane -> longest chain that contains carbonyl group
  • Indicate carbonyl group by changing -ane to -one
  • Number parent chain from direction that gives carbonyl carbon smaller number
• IUPAC name for aldehydes/ketones with -OH or -NH2 group


  • Number parent chain to give carbonyl carbon lower number
  • Indicate -OH substituent by hydroxy-
  • Indicate -NH2 substituent by amino-
  • Hydroxy and amino substituents numbered and alphabetized with other substituents
• Structural formulas


  • 2-Ethyl-3-methylpentanal
  • 3,3-Dimethylcyclohexanone
  • 2-Ethylbenzaldehyde
• Common names for aldehydes


  • Derived from common name of corresponding carboxylic acid
  • Drop "acid" and change suffix -ic or -oic to -aldehyde
  • Name each alkyl or aryl group bonded to carbonyl carbon as separate word, followed by "ketone"
• C=O bond in aldehydes and ketones


  • Polar, with oxygen bearing partial negative charge and carbon bearing partial positive charge
• Intermolecular attractions in liquid aldehydes and ketones

  • Weak attractions between partial positive charge on carbonyl carbon of one molecule and partial negative charge on carbonyl oxygen of another
  • No hydrogen bonding possible
• Boiling points of compounds

  Alkanes < ethers < aldehydes < ketones < alcohols < carboxylic acids
• Water solubility of aldehydes and ketones

  • Smaller compounds have significant water solubility
  • Solubility decreases as hydrocarbon portion increases
• Formaldehyde, acetaldehyde, and acetone are infinitely soluble in water
• Oxidation of aldehydes


  • Oxidized to carboxylic acids by variety of oxidizing agents
  • Liquid aldehydes sensitive to oxidation by O2 in air, must be protected during storage
• Oxidation of ketones


  Resist oxidation by most oxidizing agents
• Tollen's reagent test for aldehydes

  1. Reduction of Tollen's reagent (ammoniacal silver nitrate) by glucose forms silver mirror

  2. Glucose oxidized to gluconic acid
• Reduction of aldehydes and ketones

  1. Carbonyl group reduced to -CHOH or -CH2OH group by hydrogen in presence of transition-metal catalyst

  2. Reduction of aldehyde gives primary alcohol

  3. Reduction of ketone gives secondary alcohol
• Sodium borohydride (NaBH4)


  • Common laboratory reagent for reduction of aldehydes and ketones
  • Hydride ion (H:-) adds to partially positive carbonyl carbon, leaving negative charge on oxygen
  • Reaction with aqueous acid gives alcohol
• NaBH4 reduction does not affect carbon-carbon double bond or aromatic ring
• Biological reduction of aldehydes and ketones

  • Reduced form of nicotinamide adenine dinucleotide (NADH) delivers hydride ion to carbonyl carbon
  • Reduction of pyruvate by NADH gives lactate
• Addition of alcohols to aldehydes and ketones


  1. Forms hemiacetal (carbon bonded to -OH and -OR)

  2. Hemiacetals generally unstable except when hydroxyl group is part of same molecule and 5- or 6-membered ring can form
• Hemiacetal reacting further with alcohol

  1. Forms acetal (carbon bonded to two -OR groups)

  2. Acid catalyzed reaction

  3. All steps reversible, can drive equilibrium by changing conditions
• Carboxylic Acids


  A class of organic compounds containing the carbonyl group
• Carboxyl group


  The functional group of a carboxylic acid, which can be represented in any one of three ways
• Nomenclature


  1. IUPAC names

  2. For an acyclic carboxylic acid, take longest carbon chain that contains the carboxyl group as the parent alkane

  3. Drop the final -e from the name of the parent alkane and replace it by -oic acid

  4. Number the chain beginning with the carbon of the carboxyl group

  5. Because the carboxyl carbon is understood to be carbon 1, there is no need to give it a number
• Nomenclature


  • An -OH substituent is indicated by the prefix hydroxy-; an -NH2 substituent by the prefix amino-
• Nomenclature


  1. To name a dicarboxylic acid, add the suffix -dioic acid to the name of the parent alkane that contains both carboxyl groups; thus -ane becomes -anedioic acid

  2. The numbers of the carboxyl carbons are not indicated because they can be only at the ends of the chain
• Common names


  Use the Greek letters alpha (a), beta (b), gamma (g), and so forth to locate substituents
• Carboxyl group


  • Contains three polar covalent bonds; C=O, C-O, and O-H
  • The polarity of these bonds determines the major physical properties of carboxylic acids
• Vapor pressure


  • A measure of the tendency of a material to change into the gaseous or vapor state, and it increases with temperature
  • The temperature at which the vapor pressure at the surface of a liquid becomes equal to the pressure exerted by the surroundings is called the boiling point of the liquid
• Boiling point


  When a liquid is heated, its molecules obtain sufficient kinetic energy to overcome the forces holding them in the liquid and they escape into the gaseous phase. By doing so, they generate a population of molecules in the vapor phase above the liquid that produces a pressure - the vapor pressure of the liquid
• Carboxylic acids


  • Have significantly higher boiling points than other types of organic compounds of comparable molecular weight
  • Their higher boiling points are a result of their polarity and the fact that hydrogen bonding between two carboxyl groups creates a dimer that behaves as a higher-molecular-weight compound
• Carboxylic acids


  • Are more soluble in water than are alcohols, ethers, aldehydes, and ketones of comparable molecular weight
• Fatty Acids


  • Long chain carboxylic acids derived from animal fats, vegetable oils, or phospholipids of biological membranes
  • More than 500 have been isolated from various cells and tissues
  • Most have between 12 and 20 carbons in an unbranched chain
  • In most unsaturated fatty acids, the cis isomer predominates; trans isomers are rare