Alkyl Halides, Aryl Halides and Functional Groups

Alkyl Halides and Aryl Halides

• A halogen atom can replace a hydrogen atom in hydrocarbons
• Carbon atoms form covalent bonds with oxygen, nitrogen, fluorine, chlorine, bromine, iodine, sulfur, and phosphorus
• A functional group is an any atom or group of atoms that will react
• Adding a functional group creates a substance with different physical and chemical properties from the parent hydrocarbon
• R and R' represent carbon chains or rings bonded to a functional group
• An * represents a hydrogen atom, carbon chain, or carbon ring
• Double and triple bonds between carbon atoms are functional groups
• Properties can be predicted by chemical structures, even structures not previously studied

Organic Compounds and Their Functional Groups

• Halogens in group 17 of the periodic table are fluorine, chlorine, bromine, and iodine
• Halocarbon is any organic compound that contains a halogen substituent
• An Alkyl halide is an organic compound containing a halogen atom covalently bonded to an aliphatic carbon atom
• Chloromethane is an alkyl halide
• An aryl halide includes a halogen atom bonded to a benzene ring or other aromatic group
• Alkyl halides are used as refrigerants
• Chlorofluorocarbons (CFCs) were used in refrigerators and air-conditioning systems
• HFCs (hydrofluorocarbons) replaced CFCs

Naming Halocarbons

• Organic molecules get IUPAC names based on main-chain alkane structures
• A prefix indicates which halogen is present Prefix examples:
• Fluoro- for fluorine
• Chloro- for chlorine
• Bromo- for bromine
• Iodo- for iodine
• Atoms must be listed alphabetically in the name if there is more than one halogen present in the molecule
• The chain must be numbered so that the substituent that comes first alphabetically gets the lowest position number

Properties and Uses of Halocarbons

• Each alkyl chloride has a higher boiling point and a higher density than the alkane with the same number of carbon atoms.
• Boiling points and densities increase as the halogen varies from fluorine to chlorine, bromine, and iodine
• Halogens have increasing numbers of electrons farther from the halogen nucleus
• Halogen-substituted hydrocarbons have an increasing tendency to form temporary dipoles
• Alkyl halides are used as starting materials in the chemical industry, solvents, and cleaning agents
• A plastic is a polymer that can be heated and molded while relatively soft
• The plastic "vinyl" is Polyvinyl chloride (PVC)

Substitution Reactions

• The source of nearly all synthetic organic compounds is petroleum.
• Petroleum consists almost entirely of hydrocarbons, especially alkanes
• A substitution reaction is the replacement of one atom or a group of atoms in a molecule by another atom or a group of atoms
• Halogenation is the process where hydrogen atoms in alkanes are replaced by atoms of halogens
• Generic form of a substitution reaction can be X for fluorine, chlorine, or bromine, but not iodine

Alcohols

• An oxygen-hydrogen group covalently bonded to a carbon atom is a hydroxyl group (-OH)
• An organic compound with a hydroxyl group replacing a hydrogen atom is an alcohol
• The general formula for an alcoholis ROH
• Ethanol and carbon dioxide are produced by yeasts
• Ethanol is an effective antiseptic
• Ethanol can be used to:
• Swab skin before an injection
• Gasoline additive
• An important starting material for the synthesis of more complex organic compounds
• Covalent bonds from the oxygen in ethanol are at the same angle as the bonds around the oxygen in the water molecule
• Hydroxyl groups of alcohol molecules are moderately polar and are able to form hydrogen bonds with the hydroxyl groups of other alcohol molecules.

Denatured Alcohol

• Addition small amounts of noxious materials, such as aviation gasoline or other organic solvents, to create denatured alchohol
• Denaturing makes the alcohol unfit for drinking
• Alcohol is a solvent for polar organic substances

Naming Alcohol

• Rules for IUPAC naming alcohols based on alkane carbon chains:
• Name the parent carbon chain or ring first and then changing the -e at the end of the name to -ol to mean a hydroxyl group is present
• In alcohols of three or more carbon atoms, the hydroxyl group can be at two or more positions; a number is added to indicate the position
  • No numbers for cyclohexanol because all carbons in the ring are equivalent
• Prefixes are required if more than one hydroxyl group; di-, tri-, and tetra- are used before the -ol
• the full alkane including -ane name is used before the prefix
• 1,2,3-propanetriol, commonly called glycerol, is an alcohol containing more than one hydroxyl group

Ethers

• An ether is an organic compound containing an oxygen atom bonded to two carbon atoms
• The general formula for Ethers is ROR'
• Ethyl ether was used as an anasthetic
• Molecules of Ethers cannot form hydrogen bonds with each other
• Ethers are more volatile and have lower boiling points and are much less soluble in water than alcohols
• If the two alkyl groups are different, the groups are listed in alphabetical order and then followed by the word ether

Amines

• Amines contain nitrogen atoms bonded to carbon atoms in aliphatic chains or aromatic rings and have the general formula RNH2
• Chemists consider amines derivatives of ammonia (NH3)
• Indicate -NH2 (amino) group using the suffix -amine
• Designate the amino group position by number
  • Final -e dropped in of the root hydrocarbon if only one amino group: 1-butanamine
  • More than one amino group requires using prefixes di-, tri-, tetra-
• The amine aniline is used in the production of dyes
• Cyclohexylamine and ethylamine are important in pesticides, plastics, pharmaceuticals, and rubber
• Volatile amines have odors humans do not like
• Amines are responsible for many odors characteristic of dead and decaying organisms
• Putrescine and cadaverine are two amines found in decaying humans
• Sniffer dogs locate human remains using amine odors

Carbonyl Compounds

• A carbonyl group is an oxygen atom double-bonded to a carbon atom
• An aldehyde is an organic compound with a carbonyl group located at the end of a carbon chain, bonded to a carbon atom on one side and a hydrogen atom on the other
• Aldehydes have the general formula CHO ( represents an alkyl group or H)
• Aldehydes are formally named by changing the final -e of to suffix -al
• The carbonyl group in an aldehyde occurs at the end of a carbon chain, so no numbers are used in the name unless branches or additional functional groups are present.
• Aldehyde molecules cannot form hydrogen bonds, so boiling points are lower than alcohols with the same number of carbon atoms
• Water molecules can form hydrogen bonds with the oxygen atom of aldehydes, so aldehydes are more soluble in water than alkanes but not as soluble as alcohols or amines.
• Formaldehyde has been used for preservation for many years
• Benzaldehyde and salicylaldehyde are two components that give almonds their natural flavor
• the aroma and flavor of cinnamon, a spice that comes from the bark of a tropical tree, are produced largely by cinnamaldehyde

Ketones

• A ketone is an organic compound in which the carbon of the carbonyl group is bonded to two other carbon atoms
• Formula: R-CO-R'
• The simplest ketone, commonly known as acetone, has only hydrogen atoms bonded to the side carbons
• Ketones are formally named by changing the -e at the end of the alkane name to -one
• A number before the name indicates the position of the ketone group in IUPAC naming
• Ketones and aldehydes share many chemical and physical properties
• ketones do not form hydrogen bonds with each other, but they do with water molecules
• Ketones are somewhat soluble in water, and acetone is completely miscible with water

Carboxylic Acid

• A carboxylic acid is an organic compound that has a carboxyl group
• A carboxyl group consists of a carbonyl group bonded to a hydroxyl group
• Formal name is formed by changing the -ane of the parent alkane to -anoic acid. Thus, the formal name of acetic acid is ethanoic acid
• Formula represented in condensed form by writing -COOH
• ethanoic acid can be written as CH3COOH
• Simplest: HCOOH, formal name methanoic acid, commonly known as formic acid
• Methanoicacid is produced by some insects as a defense mechanism
• Carboxylic acids are polar and reactive
• Those that dissolve in water ionize weakly to produce hydronium ions and the anion of the acid in equilibrium
• Carboxylic acids ionize in water because the two oxygen atoms are highly electronegative, allowing the hydrogen proton to transfer to another atom with a pair of electrons, such as the oxygen atom of a water molecule.
• Acids such as - oxalic acid and adipic acid - have two or more carboxyl groups.called a dicarboxylic acid.
• Others have additional functional groups such as hydroxyl groups, as in the lactic acid found in yogurt.
• these acids are more soluble in water and often more acidic than acids with only a carboxyl group.

Esters

• Formed when the hydrogen or the hydroxyl group of a carboxylic acid is replaced by a different atom or group of atoms
• An ester is any organic compound with a carboxyl group in which the hydrogen of the hydroxyl group has been replaced by an alkyl group
• Formula: R-COO-R’
• The name of an ester is formed by writing the name of the alkyl group followed by the name of the acid with the -ic acid ending replaced by -ate
• methyl hexanoate is the aroma of strawberries
• ethyl butanoatecontributes to the aroma of pineapple
• Esters provide flavors and aromas

Amides

• an organic compound in which the -OH group of a carboxylic acid is replaced by a nitrogen atom bonded to other atoms
• Amides are named writing the name of the alkane with the same number of carbon atoms, and then replacing the final -e with -amide
• Amide functional group is repeated in natural proteins and some synthetic materials
• Examples of Amides: ethanamide (acetamide) and acetaminophen
• Caramide or urea
• end product in the metabolic breakdown of proteins in mammals
• used as a fertilizer and a protein supplement for ruminant animals