Chemistry EOT3 Exam Notes

Alkyl Halides and Aryl Halides

• Substituted Hydrocarbon: An organic compound where a functional group replaces one or more hydrogen atoms in a hydrocarbon.
• Substituent Group: A side branch attached to a parent hydrocarbon chain.
• Halogen: Elements from Group 17 (fluorine, chlorine, bromine, iodine).
• Halocarbon: An organic compound containing a halogen substituent, represented by the general formula RX.
  • R: Hydrocarbon chain or ring.
  • X: Halogen functional group.
• Alkyl Halide: An organic compound with a halogen atom covalently bonded to an aliphatic carbon atom.
  • Formed by replacing a hydrogen atom in an alkane with a halogen atom.
  • Example: Chloromethane (used in silicone product manufacturing).
  • Widely used as refrigerants; Hydrofluorocarbons (HFCs) replaced chlorofluorocarbons (CFCs) due to the negative effect of CFCs on the ozone layer.
  • HFCs contain only hydrogen and fluorine atoms bonded to carbon (e.g., 1,1,2-trifluoroethane or R134a).
• Aryl Halide: An organic compound with a halogen atom bonded to a benzene ring or other aromatic group.
  • Structural formula created by drawing the aromatic structure and replacing hydrogen atoms with halogen atoms.

Naming Halocarbons (IUPAC Rules)

1. Identify and name the parent chain.
2. Identify and list the substituents in alphabetical order.
3. Use number prefixes to indicate the number of times a halogen appears.
4. Number the carbon atoms in the parent chain.
5. Write the alkyl halide’s full name.

• Halogen prefixes: fluoro- (fluorine), chloro- (chlorine), bromo- (bromine), iodo- (iodine).
• Example: 4-bromo-1,2-dichlorobutane.
• Number the benzene ring in an aryl halide to give each substituent the lowest position number possible.

Properties and Uses of Halocarbons

• Alkyl chlorides have higher boiling points and densities than alkanes with the same number of carbon atoms.
• Boiling points and densities increase as the halogen changes from fluorine to chlorine, bromine, and iodine.
• This trend occurs because halogens from fluorine to iodine have increasing numbers of electrons farther from the nucleus, leading to a greater tendency to form temporary dipoles.
• Stronger dipoles lead to increased energy needed to separate molecules, thus higher boiling points.

Uses of Halocarbons:

• Primarily man-made, with few natural sources (e.g., organic iodides in humans for thyroid function).
• Alkyl halides are reactive and often used as starting materials in the chemical industry.
• Used as solvents and cleaning agents for dissolving nonpolar molecules like greases.
• Polytetrafluoroethene (PTFE): A plastic made from gaseous tetrafluoroethylene, providing a nonstick surface for kitchen items.
• Polyvinyl Chloride (PVC): A plastic that can be manufactured soft or hard, as thin sheets, or molded into objects.

Substitution Reactions

• Many halocarbons are manufactured through substitution reactions.
• The ultimate source of synthetic organic compounds is petroleum (fossil fuel consisting of hydrocarbons, especially alkanes).
• Substitution Reaction: One atom or group of atoms in a molecule is replaced by another atom or group of atoms.
  • In alkanes, hydrogen atoms can be replaced by halogen atoms (typically chlorine or bromine) in a process called halogenation.
  • Example: Halothane (2-bromo-2-chloro-1,1,1-trifluoroethane), a halogenated hydrocarbon used as a general anesthetic.
• Generic form of a substitution reaction (X can be fluorine, chlorine, or bromine, but not iodine, as iodine does not react well with alkanes).
• Halogenation: The process where a halogen atom substitutes a hydrogen atom in an alkane.

Further Substitution

• Alkyl halides can undergo further substitution reactions where other functional groups substitute the halogen atoms.
• General Alkyl Halide-Base Reaction:
  • Reacting an alkyl halide with a basic solution results in the hydroxyl group (–OH) substituting the halogen atom in the alkyl halide (R–X), forming an alcohol (R–OH).
• General Alkyl Halide-Ammonia Reaction:
  • Reacting an alkyl halide with ammonia (NH3) results in the amino group (–NH2) substituting the halogen atom in the alkyl halide (R–X), forming an alkyl amine (R–NH2).

Alcohols, Ethers, and Amines

Alcohols

• Oxygen atoms commonly form two covalent bonds to gain a stable octet.
• Functional groups in alcohols, ethers, and esters all have oxygen.
• Hydroxyl Group (–OH): An oxygen-hydrogen group covalently bonded to a carbon atom.
• Alcohol: A substituted hydrocarbon with a hydroxyl functional group (−OH).
• Hydroxyl groups are moderately polar and can form hydrogen bonds, leading to higher boiling points than hydrocarbons of similar size.
• Ethanol and carbon dioxide are produced by yeasts during sugar fermentation.
• Ethanol:
  • A gasoline additive.
  • Found in alcoholic beverages and medicinal products.
  • Used as an antiseptic before injections.
  • An important starting material for synthesizing complex organic compounds.
• Ethanol is completely miscible with water due to polarity and hydrogen bonding.
• Denatured Alcohol: Ethanol with noxious materials added to make it unfit for drinking.
• Alcohols are good solvents for polar organic substances.
  • Methanol is a common industrial solvent.
  • 2-butanol is found in some stains and varnishes.
• Names of alcohols are based on alkane names.
  • CH4 (methane) and CH3OH (methanol).
  • CH3CH3 (ethane) and CH3CH2OH (ethanol).
• IUPAC rules: name the parent carbon chain or ring first and change the -e to -ol to indicate the hydroxyl group.
• In alcohols with three or more carbon atoms, the hydroxyl group's position is indicated by a number.
  • Example: Cyclohexanol (poisonous solvent used in plastics and insecticides).
• Carbon chains can have multiple hydroxyl groups; prefixes like di-, tri-, and tetra- are used before -ol to indicate the number of hydroxyl groups.
  • Glycerol is used as an antifreeze and airplane deicing fluid.

Ethers

• Ethers are organic compounds containing an oxygen atom bonded to two carbon atoms (ROR').
• Ethyl ether was historically used as an anesthetic in surgery from 1842 until the twentieth century.
• Ethers cannot form hydrogen bonds with each other, making them more volatile and with lower boiling points than alcohols of similar size.
• Ethers are less soluble in water than alcohols because they cannot donate hydrogen atoms for hydrogen bonds.
• The oxygen atom can act as a hydrogen bond receptor for water molecules.
• Naming ethers:
  • If the two alkyl chains are identical, name the alkyl group and add the word ether.
  • If the two alkyl groups are different, list them in alphabetical order followed by the word ether.

Amines

• Amines contain nitrogen atoms bonded to carbon atoms in aliphatic chains or aromatic rings, with the general formula RNH_2.
• Amines are considered derivatives of ammonia (NH_3).
• Amines are classified as primary, secondary, or tertiary based on how many hydrogens in ammonia have been replaced by organic groups.
• Naming amines: The –NH2 (amino) group is indicated by the suffix -amine.
  • The position of the amino group is designated by a number.
  • If only one amino group is present, the final -e of the root hydrocarbon is dropped (e.g., 1-butanamine).
  • If more than one amino group is present, prefixes di-, tri-, tetra-, etc., are used.
• Aniline is used in dye production.
• Cyclohexylamine and ethylamine are used in manufacturing pesticides, plastics, pharmaceuticals, and rubber.
• Volatile amines have offensive odors associated with decaying organisms (e.g., putrescine and cadaverine).
• Specially trained animals are used to locate human remains using these odors.

Carbonyl Compounds

Carbonyl Group

• A carbonyl group is an arrangement where an oxygen atom is double-bonded to a carbon atom (C=O).
• This group is the functional group in aldehydes and ketones.

Aldehydes

• An aldehyde is an organic compound with a carbonyl group 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 RCHO, where R represents an alkyl group or a hydrogen atom.
• Aldehydes are formally named by changing the final -e of the corresponding alkane name to the suffix -al.
• The carbonyl group in an aldehyde is always at the end of the carbon chain, so no numbers are used unless branches or additional functional groups are present.
  • Methanal is commonly called formaldehyde.
  • Ethanal has the common name acetaldehyde.
• Scientists often use common names because they are familiar.
• Aldehyde molecules contain a polar, reactive structure but cannot form hydrogen bonds among themselves.
• Therefore, aldehydes have lower boiling points than alcohols with the same number of carbon atoms.
• Water molecules can form hydrogen bonds with the oxygen atom of aldehydes, making them more soluble in water than alkanes but less soluble than alcohols or amines.
• Formaldehyde has been used for preservation.
• Industrially, formaldehyde is reacted with urea to manufacture grease-resistant, hard plastic for buttons, appliance parts, automotive parts, electrical outlets, and plywood glue.
• Benzaldehyde and salicylaldehyde give almonds their natural flavor.
• Cinnamaldehyde largely produces the aroma and flavor of cinnamon.

Ketones

• A ketone is an organic compound in which the carbon of the carbonyl group is bonded to two other carbon atoms.
• 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 and including a number before the name to indicate the position of the ketone group.
• Ketones and aldehydes share many chemical and physical properties because their structures are similar.
• Ketones are polar molecules and are less reactive than aldehydes.
• For this reason, ketones are popular solvents for other moderately polar substances, including waxes, plastics, paints, lacquers, varnishes, and glues.
• Like aldehydes, ketone molecules cannot form hydrogen bonds with each other but can form hydrogen bonds with water molecules.
• Therefore, ketones are somewhat soluble in water.
• Acetone is completely miscible with water.

Carboxylic Acids

• 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.
• Acetic acid is the acid found in vinegar.
• The formal name is formed by changing the -ane of the parent alkane to -anoic acid.
  • The formal name of acetic acid is ethanoic acid.
• A carboxyl group is usually represented in condensed form by writing –COOH.
  • Ethanoic acid can be written as CH_3COOH.
• The simplest carboxylic acid consists of a carboxyl group bonded to a single hydrogen atom (HCOOH).
  • Its formal name is methanoic acid, but it is more commonly known as formic acid.
• Some insects produce formic acid as a defense mechanism.
• Carboxylic acids are polar and reactive.
• Those that dissolve in water ionize weakly to produce hydronium ions, the anion of the acid in equilibrium with water, and the unionized acid.
• Carboxylic acids can ionize in water solution because the two oxygen atoms are highly electronegative and attract electrons away from the hydrogen atom in the –OH group.
• The hydrogen proton can transfer to another atom that has a pair of electrons not involved in bonding, such as the oxygen atom of a water molecule.
• Because they ionize in water, soluble carboxylic acids turn blue litmus paper red and have a sour taste.
• Some carboxylic acids, such as oxalic acid and adipic acid, have two or more carboxyl groups.
• An acid with two carboxyl groups is called a dicarboxylic acid.
• Others have additional functional groups such as hydroxyl groups, as in the lactic acid found in yogurt.
• Typically, these acids are more soluble in water and often more acidic than acids with only a carboxyl group.

Organic Compounds Derived from Carboxylic Acids

• Several classes of organic compounds have structures in which the hydrogen or the hydroxyl group of a carboxylic acid is replaced by a different atom or group of atoms.
• The two most common classes are esters and amides.

Esters

• 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.
• 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.
• Esters are polar molecules, and many are volatile and sweet-smelling.
• Many kinds of esters are found in the natural fragrances and flavors of flowers and fruits.
  • The aroma of strawberries is due in part to methyl hexanoate.
  • Ethyl butanoate contributes to the aroma of pineapple.
• Most natural aromas and flavors are mixtures of esters, aldehydes, and alcohols.
• Some of these flavors can be imitated by a single ester structure.
• Consequently, esters are manufactured for use as flavors in many foods and beverages and as fragrances in candles, perfumes, and other scented items.

Amides

• An amide is 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 by writing the name of the alkane with the same number of carbon atoms and then replacing the final -e with -amide.
  • The amide is called ethanamide but can also be named acetamide from its common name, acetic acid.
• The amide functional group is found repeated many times in natural proteins and some synthetic materials.
• Acetaminophen contains an amide group connecting a carbonyl group and an aromatic group.
• Urea is an end product in the metabolic breakdown of proteins in mammals and is found in blood, bile, milk, and perspiration.
• When proteins are broken down, amino groups (NH_2) are removed from the amino acids.
• The amino groups are then converted to ammonia (NH_3) molecules that are toxic to the body.
• The toxic ammonia is converted to nontoxic urea in the liver.
• The urea is filtered out of the blood in the kidneys and passed from the body in urine.
• Because of the high nitrogen content of urea and its easy conversion to ammonia in the soil, urea is a common commercial fertilizer.
• Urea is also used as a protein supplement for ruminant animals, such as cattle and sheep, as they use it to produce proteins in their bodies.

Condensation Reactions

• In a condensation reaction, two smaller organic molecules combine to form a more complex molecule, accompanied by the loss of a small molecule such as water.
• Typically, the molecule lost is formed from one particle from each of the reactant molecules.
• Many laboratory syntheses and industrial processes involve the reaction of two organic reactants to form a larger organic product.
• To synthesize aspirin, two organic molecules are combined in a condensation reaction to form a larger molecule.
• In essence, a condensation reaction is an elimination reaction in which a bond is formed between two atoms not previously bonded to each other.
• The most common condensation reactions involve combining carboxylic acids with other organic molecules.
• A common way to synthesize an ester is by a condensation reaction between a carboxylic acid and an alcohol.

Other Reactions of Organic Compounds

Classifying Reactions of Organic Substances

• Classifying the chemical reactions of organic compounds makes predicting products of reactions much easier.
• Organic compounds undergo chemical reactions that can change them from an unsaturated to a saturated form and vice versa.
• These reactions differ in:
  • mechanisms (replace/add/remove)
  • kinds of atoms reacting (H2/H2O/HX)
• We can change organic compounds into other different organic compounds either by substitution or condensation reactions.
  • Substitution reaction: A chemical reaction where one atom or group of atoms replaces another atom or group of atoms.
  • Condensation reaction: A chemical reaction where two or more small organic molecules combine to form a single molecule.
• Two other important types of reactions by which organic compounds can be changed into different compounds are elimination reactions and addition reactions.

Elimination Reactions

• Alkenes are more reactive than alkanes. Changing an alkane to its corresponding alkene will make it a more reactive substance.
• This process is called elimination.
• Elimination reaction: Is when two atoms or groups of atoms are removed from two adjacent carbon atoms in a molecule to form a new molecule.
• Elimination reactions involve breaking two single bonds, mainly in saturated compounds, to produce an unsaturated compound.
• Elimination reactions can change:
  • a saturated molecule (alkane) to an unsaturated molecule (alkene) by converting a C–C single bond to a C=C double bond
  • an unsaturated molecule (alkene) to a more unsaturated molecule (alkyne) by converting a C=C double bond to a C≡C triple bond
• One of the products of the elimination reactions is a small molecule.
• A small molecule can be:
  • a hydrogen gas molecule (H_2)
  • a water molecule (H_2O)
  • a hydrogen halide molecule (HX)
• Based on the kind of atoms or groups of atoms that leave the molecules during elimination reactions, there are three types of elimination reactions:

Dehydrogenation Reactions

• A dehydrogenation reaction is a chemical reaction that involves the removal of two hydrogen atoms from an alkane.
• The products of this reaction are:
  • an unsaturated molecule
  • a hydrogen gas molecule (H_2)
• Ethene, the starting material for the playground equipment, is produced by the dehydrogenation of ethane.
• Low-density polyethylene (LDPE) is made from gaseous ethene under high pressure in the presence of a catalyst.
• LDPE is used for playground equipment because it is easy to mold into various shapes, it is easy to dye into many colors, and it is durable.
• The name polyethylene comes from ethylene, which is the common name for ethene.

Dehydration Reactions

• A dehydration reaction is a chemical reaction that involves the removal of a hydrogen atom and a hydroxyl group (–OH) from an alcohol.
• The products of this reaction are:
  • an unsaturated molecule
  • a water molecule (H_2O)
• A dehydration reaction is an elimination reaction in which the atoms removed form water.

Dehydrohalogenation Reactions

• A dehydrohalogenation reaction is a chemical reaction that involves the removal of a hydrogen atom and a halogen from an alkyl halide.
• The products of this reaction are:
  • an unsaturated molecule
  • a hydrogen halide (HX) molecule (where X = F, Cl, or Br)

Addition Reactions

• An addition reaction is when two atoms or groups of atoms are added to an unsaturated molecule, forming a single product.
• Addition reactions typically involve double-bonded carbon atoms in alkenes or triple-bonded carbon atoms in alkynes.
• Addition reactions occur because double and triple bonds have a rich concentration of electrons.
• Therefore, molecules and ions that attract electrons tend to form bonds that use some of the electrons from the multiple bonds.
• Based on the kind of atoms or groups of atoms added to the unsaturated molecules during addition reactions, there are four types of addition reactions:

Hydrogenation Reactions

• A hydrogenation reaction is a chemical reaction that involves the addition of two hydrogen atoms to an unsaturated compound.
• The product of this reaction is a saturated compound.
• Hydrogenation of unsaturated compounds needs a catalyst to proceed.
• Examples of catalysts used in hydrogenation reactions include
  • platinum (Pt),
  • palladium (Pd),
  • and nickel (Ni).
• Catalysts are usually needed in the hydrogenation of alkenes because the reaction’s activation energy is too large without them.
• Catalysts such as powdered platinum or palladium provide a surface that adsorbs the reactants and makes their electrons more available to bond to other atoms.
• Hydrogenation reactions are commonly used to convert the liquid unsaturated fats found in oils from plants such as soybean, corn, and peanuts into saturated fats that are solid at room temperature.
• These hydrogenated fats are then used to make margarine and solid shortening.

Hydration Reactions

• A hydration reaction is a chemical reaction that involves the addition of a hydrogen atom and a hydroxyl group (–OH) from a water molecule to an unsaturated compound.
• The product of this reaction is
  • a saturated compound.
• A hydration reaction is the opposite of a dehydration reaction.

Hydrohalogenation Reactions

• A hydrohalogenation reaction is a chemical reaction that involves the addition of a hydrogen atom and a halogen from a hydrogen halide molecule to an unsaturated compound.
• The product of this reaction is
  • a saturated compound.

Halogenation Reactions

• A halogenation reaction is a chemical reaction that involves the addition of two halogen atoms from a halogen molecule to an unsaturated compound.
• The product of this reaction is
  • a saturated compound.