Chapter 15: Organic Compounds and the Atomic Properties of Carbon

Homework:8,9,15,20,21,24,25,30,31,36,43,44,47,48,51,60,61,69,70,76,83,85,87,97,104,105

Organic chemistry originally thought of as the chemistry of substances that came from living things, and that organic chemicals were imparted with an innate ‘vital force’. The fall of the vital force theory came when urea, a simple organic substance, was synthesized from nonliving material.

CO₂ + 2 NH₃ à NH₂CONH₂ + H₂O

Organic chemistry is now defined as the study of carbon-based compounds and their reactions.

Critical Knowledge

Number of bonds for elements in organic molecules:

C = 4, N = 3, O = 2, H = 1, Halogen = 1

Hybridization     bonding              electron distribution    bond angle
         sp³         single bonds          tetrahedral                109.5
         sp²         double bond          trigonal planar            120
         sp          triple bond             linear                       180

Hydrocarbons: Alkanes and Cycloalkanes

Nomenclature

CH₄ Methane CH₄

CH₃CH₃ Ethane C₂H₆

CH₃CH₂CH₃ Propane C₃H₈

CH₃CH₂CH₂ CH₃ Butane C₄H₁₀ CH₃(CH₂)₂CH₃

CH₃CH₂CH₂ CH₂ CH₃ Pentane C₅H₁₂ CH₃(CH₂)₃CH₃

CH₃CH₂CH₂ CH₂ CH₂ CH₃ Hexane C₆H₁₄ CH₃(CH₂)₄CH₃

CH₃CH₂CH₂ CH₂ CH₂ CH₂ CH₃ Heptane C₇H₁₆ CH₃(CH₂)₅CH₃

CH₃CH₂CH₂ CH₂ CH₂ CH₂ CH₂ CH₃ Octane C₈H₁₈ CH₃(CH₂)₆CH₃

CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₃ Nnonane C₉H₂₀ CH₃(CH₂)₇CH₃

CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₃ Decane C₁₀H₂₂CH₃(CH₂)₈CH₃

Substituent Groups

CH₃- Methyl Cl- Chloro

CH₃CH₂- Ethyl Br- Bromo

CH₃CH₂CH₃ Propyl I- Iodo

CH₃CH₂CH₂ CH₂- Butyl F- fluoro

CH₃CH₂CH₂ CH₂ CH₂- Pentyl -NO₂ Nitro

CH₃CH₂CH₂ CH₂ CH₂ CH₂- Hexyl

Consider the following molecule and name it using the following procedures.

3,3,4-tribromo-6-chloro-2-methyloctane

1 When naming a hydrocarbon, you find the longest continuous carbon chain and number it giving the lowest possible numbers to the substituent groups. This longest chain is called the parent molecule.

2 Give the name of substituent groups in alphabetic order giving the number of the carbon that EACH substituent group is attached to, and indicate the number of EACH type of substituent by using the prefixes: di, tri, tetra, penta, hexa, hepta, octa, nona, deca etc. Commas go between numbers and dashes go between numbers and words. Try these:

3 When hydrocarbons are cyclic, that is the ends are attached to form a closed carbon ring, the prefix cyclo- is given to the parent hydrocarbon. Numbers are given to give the lowest possible numbers to the substituents.

Problem 1: What is the general formula for linear alkanes. What is the general formula for cyclic alkanes.

Problem 2: Give all the possible straight chain alkane isomers for C₆H₁₄ and name each.

Problem 3: Give all the possible cycloalkane isomers for C₆H₁₂ and name each.

Alkenes

Alkenes are hydrocarbons having carbon-carbon double bonds.

CH₂=CH₂ Ethene

CH₂=CHCH₃ Propene

CH2=CHCH₂CH₃ 1-Butene

CH₃CH=CHCH₃ 2-Butene

CH₂=CHCH₂CH₂CH₃ 1-Pentene

CH₃CH=CHCH₂CH₃ 2-Pentene

CH₂=CHCH₂CH₂CH₂CH₃ 1-Hexene

CH₃CH=CHCH₂CH₂CH₃ 2-Hexene

CH₃CH₂CH= CHCH₂CH₃ 3-Hexene etc.

When naming alkenes the lowest number is given to the double bond in the molecule. Double bonds take precedence over other substituent groups.

Problem 4: Name the following:

CH₃CH₂CH=CHCHClCCl₂CH₂CHClCH₃

CH₃CH₂CHClC(CH₃)ClCCl₂CH=CH₂

CH₃CH₂CH= CHCHClCCl₂CH₂CCl=CH₂

Since carbon-carbon double bonds can’t rotate, stereoisomerisms (cis-trans) isomers exists.

Cis-1,2-dichloro ethene Trans-1,2-dichloro ethene

Problem 5: Give all possible alkene isomers for C₆H₁₂ and name each isomer.

Problem 6: What is the general formula for alkenes?

Problem 7: What is the general formula for a cycloalkene?

Problem 8: What is the general formula for a diene?

Aromatic Hydrocarbons

Aromatic hydrocarbons are cyclic hydrocarbons having alternating double bonds whose number of p-electrons is 4n+2 where n can be 0,1,2,3,4...

Benzene

Each sp² hybridized carbons has a leftover p-orbital in which 3 pairs of electrons exist above and below the plane of the carbons in a p-bonding network. This p-network delocalizes (spreads out) the electrons thus reducing the energy of the system. The two resonance forms of benzene are shown above; however, neither is correct since the electron waves are spread out evenly throughout the p-system.

When naming substituted benzenes, the lowest number is given to the substituent group(s), the names of the substituent groups is given in alphabetic order and the name benzene or the particular benzene derivative is given last.

Benzene Derivatives Ø = C₆H₅ (Phenyl group)

Ø-OH Phenol Note: The lowest number is given to

Ø-NH₂ Analine the functional group.

Ø-CH₃ Toluene

Ø-CHO Benzaldehyde

Ø-CO₂H Benzoic acid

Problem 9: Name the follwoing:

Another nomenclature that is particular to benzene derivatives is the ortho, para, meta designation. Ortho indicates the #2 position relative to another substituent group or functional group. Meta indicates the #3 position relative to another substituent group or functional group. Para indicates the #4 position relative to another substituent group or functional group. When giving this designation o-, p- and m- are used in front of the substituent group’s name.

Problem 10: Give two names for each of the following.

Derivatives of Hydrocarbons: Functional Groups

General Formula General Class Example Example name

R-X X= Cl, Br, I, F Organic halide CH₃CH₂-Br Ethyl bromide

R-OH Alcohol CH₃CH₂-OH Ethanol or Ethyl Alcohol

R-O-R Ether CH₃CH₂-O-CH₂CH3Diethyl ether

R-COH Aldehyde CH₃CH₂-COH Ethanal

R-COR’ Ketone CH₃CH₂-CO-CH₂CH₃ 3-pentanone

R-COOH Carboxylic acid CH₃CH₂-COOH Propanoic acid

R-COOR’ Ester CH₃COOCH₃ Methylacetate

R-NH₂, R-N, R-N Amine CH₃CH₂-NH₂ Etylamine

R-CON Amide CH₃CONHCH₃ N-methylacetamide

Alcohols

Alcohols are hydrocarbons having an -OH group. Alcohols have three general classes: Primary 1°, secondary 2° and tertiary 3°.

1° 2° 3°

Alcohols can be formed by the addition of water across a double bond. Under the reaction conditions, the -OH group is added to the MOST SUBSTITUTED carbon and the hydrogen is added to the LEAST SUBSTITUTED carbon when there is a choice. This is called Markovnikov's rule.

CH₃CH=CH₂ + H₂O + CH₃CHOHCH₃

To add the -OH to the least substituted carbon, anti-Markovnikov, the hydroboration-oxidation method is used.

CH₃CH=CH₂ CH₃CH₂CH₂OH

Ethers

Ethers have the general formula R-O-R’. The common nomenclature for ethers consists of alphabetically naming the hydrocarbon groups making up the ether using the -yl ending followed by the word ether.

The IUPAC nomenclature for ethers consists of the root of the shorter hydrocarbon then -oxy- followed by the name of the longest hydrocarbon.

Problem 11: Name the following ethers using the common nomenclature and IUPAC nomenclature.

CH₃OCH₂CH3 CH₃CH₂OCH₂CH₂CH₃ CH₃CH₂CHBrOCH₂CH₂CH₃

Ethers as a class tend to be relatively unreactive. Ethers are prepared by the reaction of sodium with an alcohol to form an alkoxide ion, which is then reacted with another alcohol to produce the ether.

2CH₃OH + 2Na à 2CH₃O^-Na⁺ + H₂

CH₃O^- + CH₃CH₂OH à CH₃OCH₂CH₃

Aldehydes

Aldehydes have the general form RCHO with a carbonyl group (-C=O) at the end of the chain. The nomenclature for aldehydes names the root first followed by -al.

Problem 12: Name the following molecules.

CH₃ CH₂CHO CH₃ CHO CH₃ CH₂CH₂ CHO

Aldehydes are made by gentle oxidation of 1° alcohols.

CH₃ CH₂OH CH₃CHO

Ketones

Ketones have a carbonyl group not at the end of a chain. Ketones are made by oxidation of 2° alcohols.

The nomenclature for ketones is similar to that of the alcohols but an -one ending is given the ketone.

Problem 13: Name the following molecules.

Carboxylic Acids

Carboxylic acids are organic acids having the general formula RCOOH, and has the structure . Carboxylic acids are formed by the vigorous oxidation of alcohols.

CH₃CH₂CH₂CH₂OH CH₃CH₂CH₂COOH

The nomenclature for the carboxylic acids is the same as the aldehydes except for the root is followed by -oic acid.

Problem 14: Name the following molecules.

CH₃CH₂CH₂CH₂CH₂COOH CH₃COOH CH₃CH₂CH₂COOH

Esters

Esters are the condensation product of the reaction of alcohols and acids, and have the structure .

CH₃CH₂CH₂COOH + CH₃CH₂OH CH₃CH₂CH₂COOCH₂CH₃

Esters are generally sweet smelling molecules with distinct odors. The nomenclature for the esters names the alcohol first followed by the name of the ion of the acid.

Problem 15: Name the following molecules.

CH₃COOCH₂CH₃

CH₃CH₂COOCH₂CH₃

CH₃CH₂COOCH₂CH₂CH₂CH₃

Oxidation Reduction Reactions

Alcohols are oxidized to aldehydes and ketones under mild conditions. Under more strenuous conditions (higher temperature and stronger oxidizing agents) they are oxidized to carboxylic acids.

1° CH₃CH₂CH₂OH CH₃CH₂CHO CH₃CH₂COOH

2° CH₃CHOHCH₃ CH₃COCH₃ NR

3° (CH₃)₃COH NR

Saponification

Saponification is the making of soap from the treatment of fats and oils with strong base. Glycerol stearate hydrolyzes in base to give glycerol and sodium stearate. The long chain stearate ion has a hydrophyllic end and a lipophyllic end. The lipophyllic end dissolves into oils and grease leaving the hydrophyllic end exposed to the water forming a micelle which can be emulsified into the water.

Organic Compounds Containing Nitrogen

Amines are classified the same way that alcohols are.

1° 2° 3°

N-butyl amine Ethylmethy amine trimethyl amine

Amines are similar to ammonia since they have a free pair of electrons and can readily react with hydronium ion to form ions.

CH₃CH₂CH₂CH₂NH₂ + H⁺ à CH₃CH₂CH₂CH₂NH₃⁺ butyl ammonium ion

Polymers

Polymer means many unit. Polymers are formed by several methods.

Addition polymerization occurs when a free radical usually from a peroxide reacts with a double bond to set up a chain reaction.

RO^. + RCH=CHR’ à ROCHR-CHR’^.

ROCHR-CHR’^. + nRCH=CHR’ à RO-(RCH-CHR’)_n+1-

Condensation polymerization occurs when a dicarboxylic acids reacts with either a dialcohol or a diamine giving a polyester or polyamide respectively.

nHOCH₂CH2OH + nHOOCCH₂CH₂CH₂COOH à

-(OCH₂CH₂OOCCH₂CH₂CH₂CO)-_n + 2nH₂O

nHOOCCH₂CH₂COOH + nNH₂CH₂CH₂NH₂à

-(OCCH₂CH₂CONHCH₂CH₂NH)-_n + 2nH₂O

Problem 16: Show the reaction for the formation of the polyamide nylon-66.

Biological Macromolecules

Sugar Monomers