Organic Chemistry

IUPAC rules: prefix (substituents) - parent (# of carbons) - suffix (what family)

Alkanes

steps for naming alkanes:

1. name the main chain (the longest continuous chain of carbons)
2. number the carbon atoms in the main chain
   • start at the end closest to the first substituent
3. identify and number the branching substituent
4. write the name as a single word
   • use hyphens to separate different prefixes and commas to separate numbers
   • list substituents in alphabetical order

properties of alkanes

• called paraffins since they don’t react as most chemicals
• will burn in a flame producing carbon dioxide, water, and heat
• react with Cl2 in the presence of light to replace H’s with Cl’s
• boiling points and melting points increase as size of alkane increases
• forces between molecules are weak

reactions of alkanes

cracking: large alkane + hydrogen gas → smaller alkane

reforming: small alkane → larger alkane + hydrogen gas

substitution (halogenation): replace H with a halogen atom

• initiated by addition of energy in the form of heat or ultraviolet light

combustion: hydrocarbon + oxygen → carbon dioxide + water

• all hydrocarbons undergo combustion

cycloalkanes - alkanes that have carbon atoms forming a ring

steps for naming cycloalkanes:

1. count the number of carbon atoms in the ring and the number in the largest substituent chain
   • if the number of carbon atoms in the ring is equal or greater than the number in the substituent the compound is named as an alkyl-substituted cycloalkane

properties of cycloalkanes

• melting points are affected by the shapes and way the crystals pack
• don’t change uniformly

isomers: different molecules with the same molecular formula

structural isomers: different pattern of atom attachment

Alkenes and Alkynes

alkenes: contain a double bond (C=C)

• one double bond = CnH2n
• have straight chains and are unsaturated
• polyunsaturated = many double bonds
• much more reactive than alkanes

steps for naming alkenes:

1. find the longest continuous carbon chain containing the double bond
2. identity the substituents
3. number the chain from the end closest to the double bond
4. write the name in the following order:
   • substituents in alphabetical order
   • number of first carbon double bond
   • name of main chain
   • end with -ene

alkynes: contain a triple bond

• one triple bond = CnH2n-2
• have straight chains and are unsaturated
• more reactive than alkenes

steps for naming alkynes:

1. find the longest continuous carbon chain that contains the triple bond
2. identify the substituents
3. number the chain from the end closest to the triple bond
4. write the name in the following order:
   • substituents in alphabetical order
   • number of first carbon triple bond
   • name of main chain
   • end with -yne

geometric isomerism: result of rotations around the double bond being highly restricted

• different molecules of groups have different spatial orientation about the double bond
• cis isomerism: groups are bonded on the same side
• trans isomerism: groups are bonded on opposite sides

Aromatic Hydrocarbons

aromatic hydrocarbons: contain a ring structure with a series of alternating single and double bonds in a delocalized arrangement

• in simple aromatic compounds, the benzene ring is the parent chain
• if the attached benzene group is not easily named the benzene ring is the attached branch, called the phenyl group

numbering carbons on the benzene ring:

• 1,2 - ortho (o)
• 1,3 - meta (m)
• 1,4 - para (p)

Reactions of Hydrocarbons

substitution reaction: the hydrogen atoms in an alkane may be substituted by a halogen such as F2, Cl2, Br2

• F2 reacts vigorously with alkanes
• Cl2 and Br2 require heat or ultraviolet light to react
• Product is a halogenated alkane of an alkyl halide

addition reaction: adding a molecule across the multiple bond (for alkenes and alkynes)

hydrogenation: adding H2

• converts unsaturated molecule → saturated
• alkene/alkyne + H2 → alkane

halogenation: adding X2 where X = F, Cl, Br, I

hydrohalogenation: adding HX where HX is polar

• when adding a polar reagent to a double or triple bond the positive part attaches to the carbon with the most H’s

hydration: adding water

• converts unsaturated hydrocarbon → alcohol

Markovnikov’s rule: in the addition of HX to alkene, the H attaches to the carbon with the most H’s, and the X attached to the end with the most alkyl substituents

aromatic compounds: have chemical reactions between those of alkanes and alkenes

• undergo substitution reactions
  • substitution reactions with cyclohexane and bromine occur much slower and requires addition of heat

Organic Halides

organic halides: a group of compounds commonly used as refigerants (CFC’s) and non-stick coating (Teflon)

• many organic halides are toxic and/or carcinogenic

properties of organic halides:

• the bonds between the carbon and halogens are more polar than those between carbon and hydrogen
• alkyl halides are more polar than their hydrocarbon parents
• they are more soluble in polar solvents than their hydrocarbon parents and have higher boiling points
• when a compound such as propane reacts with a halogen a mixture of compounds containing 1,2,3 or more halogens form
• the more halogenated a compound is the more polar it is

preparing organic halides:

• alkenes and alkynes readily add halogens or hydrogen halides to their double or triple bonds
• Markovnikov’s rule applies when hydrogen halides are reactants
  • alkene/alkyne + hydrogen halide → organic halide
• compounds with benzene rings have a substitution reaction
• elimination reaction: a hydroxide ion is used to eliminate a hydrogen and halide ion from adjacent carbon atoms to form a double bond making an alkene
  • alkane + OH → alkene + water + halogen

Alcohols and Ethers

alcohol: a water molecule with one of the hydrogen atoms replaced with an alkyl group (R - O - H)

there are three classification alcohols:

1. primary alcohols: hydroxide is attached to an alkyl group attached to one other alkyl group

2. secondary alcohols: hydroxide is attached to an alkyl group attached to two other alkyl groups

3. tertiary alcohols: hydroxide is attached to an alkyl group attached to three other alkyl groups

   

cyclic alcohols: compounds containing cyclic alkanes or aromatic hydrocarbons attached to a hydroxyl group

properties of alcohols:

• much higher boiling points than parent alkanes
• more soluble than parent alkanes
• properties are due to H-bonding among molecules

reactions involving alcohols:

hydration: reacting alkenes with water in the presence of a catalyst results in an alcohol

• alkene + water → alcohol
• OH is found on the second carbon due to Markovnikov’s rule

combustion: alcohols undergo complete combustion to produce carbon dioxide and water

ethers: a water molecule with both of the hydrogen atoms replaced with alkyl groups (R - O - R) or (R - O - R’)

properties of ethers:

• don’t form hydrogen bonds since they lack an OH group
• more polar than hydrocarbons because of the dipole arising from their C-O-C bonds

naming ethers: add oxy to the prefix of the smaller hydrocarbon group and join it to the name of the larger hydrocarbon group

preparing ethers from alcohols:

• condensation: ethers are formed by the reaction of 2 alcohols and the elimination of a water molecule
  • alcohol + alcohol → ether + water

Aldehydes and Ketones

aldehydes: consist of an alkyl group bonded to a carbonyl group with a hydrogen atom on the end

ketones: consist of two alkyl groups attached to a central carbonyl group

naming aldehydes and ketones:

• aldehyde: name ends with -al
• ketones: name ends with -one
• if the carbon chain has 5 or more carbon atoms a number is needed to indicate the location of the carbonyl group

properties of aldehydes and ketones:

• lower boiling points and less soluble than corresponding alcohols
• more soluble than corresponding alkanes
• aldehydes and ketones can mix with both polar and non-polar substances
  • allows non-polar materials to be mixed with polar materials

preparing aldehydes and ketones from alcohols by oxidation reaction:

• oxidation: reactions involve a loss of electrons
  • the element or compound that loses electrons is oxidized
  • the element or compound that gains electrons is reduced
• controlled oxidation of alcohols results in aldehydes and ketones
  • the reactive oxygen atoms are supplied by oxidizing agents (O)
  • when primary alcohol is oxidized, an H atom remained on the C atom and an aldehyde is produced
  • primary alcohol + (O) → aldehyde + water
  • when secondary alcohol is oxidized, the carbonyl group that forms is attached to two alkyl groups forming a ketone
  • secondary alcohol + (O) → ketone + water
  • tertiary alcohols don’t react since there’s no hydrogen available for oxidation
• hydration: hydrogen can be added to the carbonyl group in aldehydes and ketones
  • high temperatures and catalysts are required for this reaction
  • this is the reverse of the controlled oxidation of alcohols

Carboxylic Acids and Esters

carboxylic acid: characterized by the presence of carboxyl functional groups (R-COOH)

naming carboxylic acids:

• the carboxyl group is made up of a hydroxyl (OH) bound to the C atom on a carbonyl group
• the main chain is the longest chain containing the carboxyl group
  • ends with -oic acid
• when naming multiple carboxyl groups the suffix -dioic is used
• when more than two carboxyl groups are present, all COOH groups may be named as substituents on the parent chain
  • the parent chain doesn’t include the carboxylic atoms

properties of carboxylic acids:

• highly polar molecules
  • the polarity of the carboxyl group makes carboxylic acids soluble in water
  • chains longer than ten carbons insoluble in water
• higher boiling points than their corresponding alkanes
• smaller members are soluble in water, larger carboxylic acids are relatively insoluble
• conduct electricity
• react with organic bases in neutralization reactions
• short chain carboxylic acids are liquids at standard temperature
• long chain carboxylic acids are waxy solids

preparing carboxylic acid:

• when alcohol is mildy oxidized, an aldehyde is produced
• if this aldehyde is oxidized further a carboxylic acid is produced
  • alcohol + (O) → aldehyde
  • aldehyde + (O) → carboxylic acid

ester: similar to carboxylic acids but th eH atom in the acid is replaced with another alkyl group (R - COO - R)

naming esters:

• the name of an ester has 2 parts
  • first part: the name of the alkyl group used in the esterification process
  • second part: the name of the acid
• the ending of the acid name change from -oic acid to -oate

properties of esters:

• the presence of the carbonyl group make esters somewhat polar
  • esters are less polar than corresponding carboxylic acids because they lack an OH group capable of H bonding
• they are less soluble in water with lower melting and boiling points than corresponding alcohols and carboxylic acids
• smaller esters are liquid at standard temperatures while longer esters are insoluble

reactions of esters:

• esterification: carboxylic acid + alcohol → ester + water
  • alcohol acts as an organic base and carboxylic acid acts as an acid
  • the ester formed is considered an organic salt
• hydrolysis: reverses esterification by reacting the ester with an acid or base
  • ester + acid/base → acid + alcohol
  • a bond is broken by the addition of water resulting in two or more products

Amines and Amides

amines: ammonia with one to all of its hydrogens substituted by alkyl groups

there are three classifications of amines:

1. primary amine: one hydrogen is substituted with an alkyl group
   • prepared by reacting ammonia with an alkyl halide
   • ammonia + alkyl halide → primary amine + hydrogen halide
2. secondary amine: two hydrogens are substituted with alkyl groups
   • prepared by reacting a primary amine further with an alkyl halide
   • primary amine + alkyl halide → secondary amine + alkyl halide
3. tertiary amine: all three hydrogens are substituted with alkyl groups
   • prepared by reacting a secondary amine further with an alkyl halide
   • secondary amine + alkyl halide → tertiary amine + alkyl halide

naming amines:

• amines are nitrogen derivatives of an alkane
• amines can also be named as alkyl derivatives of ammonia
• diamines: molecules with 2 amino groups
• for secondary and tertiary amines include the N-prefix to show the substituted groups on the amine

properties of amines:

• primary and secondary amines are very polar due to the N-H bond which allows them to H-bond with each other
  • tertiary amines don’t have N-H bonds and can’t H-bond
• higher boiling and melting points than similar-sized ethers and alkanes
• smaller amines are soluble in water
• N-C and N-H bonds are more polar
• amines share a lower boiling point than alcohols of similar size because N-H bonds are less polar than O-H bonds

when amines are created using alkyl halides, a mixture of primary, secondary, and tertiary amines result

• can separate the different amines through boiling point

amides: hydrocarbon that contains a carbonyl group bonded to a nitrogen atom

• similar to esters but the N atom replaces the O atom in the chain of an ester
• they are the backbone of all protein molecules
• in proteins amide bonds are called peptides

properties of amides:

• amides have a polar carbonyl group and amides with a least one NH group can form strong hydrogen bonds among themselves
• higher boiling points that their corresponding hydrocarbon derivatives
• weak bases that are insoluble in water
  • low molecular weight amides are slightly soluble
• can be hydrolyzed in acidic or basic conditions to produce a carboxylic acid and an amine

naming amides:

• the first part of an amide’s name comes from the amine
• the second part of the name comes from the acid
• ends with the suffix -amide
• if one or more alkyl groups is attached to the N atom the upper case N is used to clarify the location

preparing amides:

• condensation: carboxylic acids react with ammonia or primary or secondary amines to produce amides
  • carboxylic acid + ammonia → amide + water
  • tertiary amines don’t undergo condensation reactions since they lack the extra H atoms needed to make water
• amides can also be made with primary amines and carboxylic acids by condensation reactions
  • carboxylic acid + primary amine → amide + water

Synthetic Addition Polymers

polymer: made up of a group of monomers (usually 10 or more)

• monomer: a hydrocarbon derived molecule
• polymers may contain thousands of individual monomers, the subscript n is used to indicate the number of repeating units

polyethylene: a polymer of ethene

• under certain conditions alkenes undergo addition reactions with other alkenes
• the double bond in each alkene changes into a single bond freeing an unbonded electron to form a single bond with other ethene monomers

addition polymerization: consists of three stages (initiation, propagation, and termination)

• an initiating molecule with an unpaired electron forms a bond with one of the carbonatoms in the double bonded monomer
  • this yields an unpaired electron on the other end of the monomer
• this electron can then form covalen bonds with another group
  • the reaction continues/propigates
• the chain grows until two unpaired electrons combine forming a covalent bond that links the growing chains together

properties of plastics:

• plastics are chemically unreactive because chemically active unsaturated alkenes have been converted into unreactive saturated carbon chains
• the strong covalent bonds make the structure very stable
• most intermolecular forces are Van der waals forces but because the molecules are so large these forces are very strong

strengthening polymers with cross-linking:

• alkenes with double bonds (-dienes) are monomers for several polymers
  • these polymers often end in -ene
• cross-linking occurs between -dienes because the second double bond allows for the formation of covalent bonds between different chains of monomers

Synthetic Condensation Polymers

dimers: formed with molecules with functional groups react with other molecules

condemnation polymers: when monomers join end to end in ester or amide linkages they form polyesters and polyamides

polyesters: a polymer of carboxylic acids and alcohols

• when condensation reactions are repeatedly used to join carboxylic acids and alcohols, a polyester is formed
  • uses a dicarboxylic acid and a diol
  • the acids donates the OH, the alcohol donates the H

polyamides: a polymer of carboxylic acids and amines

• they are condensation polymers consisting of many amides
• the monomers must contain carboxyl groups, amine groups, or one of each