Chapter 16Organic Chemistry

In this chapter, we will explore basic organic concepts including nomenclature, structure, and functional groups.

What Is an Organic Compound?

● Organic vs Inorganic● Vital Force● Synthesis of urea● Carbon chemistry

Most naturally occurring or synthesized compounds.

What Is an Organic Compound?

● Carbon chemistryC-C covalent bonds

C bonds with other nonmetals

Strong

Multiple bonds

The Saturated Hydrocarbons or Alkanes

● CxHy

● If y = 2x+2, compound is a saturated hydrocarbon, also known as an alkane.

● Tetravalent C

The Saturated Hydrocarbons or Alkanes

● Straight Chain● Branched Chain● Isomers

Constitutional

Others….later.

Rotation Around C-C Bonds

● ConformationsEclipsed

Staggered

The Nomenclature of Alkanes

● Longest chain● Substituents● Number the chain.● Prefixes (di, tri, ...)● Alphabetical substituents

The Unsaturated Hydrocarbons: Alkenes and Alkynes

● Hydrocarbons with C=C or C C are unsaturated.

● Alkene for double bond, alkyne for triple bond.● Unsaturated because they do not contain the

maximum possible H per C.

The Unsaturated Hydrocarbons: Alkenes and Alkynes

● Nomenclature-ane to -ene or -yne.

Number C atoms and indicate where multiple bond is located.

Aromatic Hydrocarbons and Their Derivatives

● Benzene, C6H6, prototypical.

● Structure was a mystery for a long time.Kekule’s solution.

Resonance structures.

Aromatic Hydrocarbons and Their Derivatives

● Monosubstituted benzenesToluene, phenol, etc.

● Disubstituted benzenesOrtho, Meta, Para

The Chemistry of Petroleum Products

● Natural gas (mostly methane)Typically distributed by pipeline

● Crude oilMixture of hydrocarbons

– Thermal reforming, cracking– Catalytic reforming, cracking

Used to increase octane number.

The Chemistry of Coal

● Complex solidC137H97O9NS

C240H90O4NS

The Chemistry of Coal

Figure 16.2

The Chemistry of Coal

● Large US supply● Prefer liquid fuels over solid fuels

Converted to synthetic gas– …on to methanol or other liquid fuels.

● Fischer-Tropsh reaction Liquid hydrocarbons from coal.

Functional Groups

● The presentation of organic reactions is organized around functional groups.

● As an example, the double bond in an alkene is a functional group.

● There are many others.

Functional Groups

Table 16.5 and Table 16.6

Oxidation-Reduction Reactions

● Already discussed these in Chapter 12.● Oxidation numbers discussed in Section

5.16● Organic redox can be characterized by

Changes in oxidation numbers, or

Changes in number of H atoms present, or

Changes in number of O atoms present.

Oxidation-Reduction Reactions

Table 16.7

Oxidation-Reduction Reactions

● For example, carbon monoxide to carbon dioxide is an oxidation

● …methanol to methane is a reduction.

Alkyl Halides

● Formed from alkane and halogen in the presence of UV light.

● Chain-reaction mechanism

Alkyl Halides

● Chain reaction mechanismInitiation

Propagation

Termination

Alcohols and Ethers

● Alcohol, ROH, is a functional group.● Names end in ol.

Also common names such as wood alcohol.● Classified as primary, secondary, or

tertiary.● Are Brønsted acids.

Alcohols and Ethers

● Conjugate base of alcohol is alkoxide.● Alcohol related to water by replacement of

one H.● Replace both Hs in water and get ether.

Alcohols and Ethers

● Ethers, ROR’.● Alcohols H bond, ethers do not.

Affects bp.

Affects solubility in water.● Ethers are an example of aprotic solvents.

Aldehydes and Ketones

● Primary Alcohol that has be dehydrogenatedCH3CH2OH → CH3COH

● If alcohol is secondary, ketone results.RC(OH)HR’ → RCOR’

Aldehydes and Ketones

● NomenclatureAldehydes named from corresponding carboxylic acid

Ending with al.

Aldehydes and Ketones

● NomenclatureKetones named with two alkyl groups plus ketone.

ethyl methyl ketone

Reactions at the Carbonyl Group

● RR’C=O has negative end (O) and positive end (C).

Electrophiles are attracted to O.– For example, H+.

Nucleophiles are attracted to C.– For example, alkoxide.

Carboxylic Acids and Carboxylate Ions

● OH attached to carbonyl C makes a carboxylic acid, -COOH.

● Carboxylate ion, -COO-.Resonance structures

● Names end in -oic acid.● Common names

Carboxylic Acids and Carboxylate Ions

Table 16.8

Esters

● Carboxylic acid plus alcohol produces ester plus water.

● Other more efficient methods to prepare esters.

● Name also includes product of strong acid and alcohol

Carboxylic acid esters are RCO2R’.

Amines, Alkaloids, and Amides

● Ammonia with one or more H replaced with alkyl.

● Like alcohols, have primary, secondary, and tertiary.

● Name has -amine at end.● Amines are bases, just like ammonia.

Amines, Alkaloids, and Amides

● To improve water solubility, ammonium salts prepared.

● Amides are a combination of carboxylic acids and amines.

Produced via acyl chloride and amine– RCOCl + 2R’NH2 → RCONHR’+ R’NH3Cl-

● Alkaloids isolated from plants…

Amines, Alkaloids, and Amides

Figure 16.6

Alkene Stereoisomers

● Already discussed constitutional isomers in section 16.2

● Another type of isomer is called stereoisomer.

cis and trans are stereoisomers.● Not all alkenes have cis and trans

isomers.

Alkene Stereoisomers

● cis and trans not always enough to describe alkene stereoisomer.

E and Z methods more versatile.– Substituent atoms prioritized by atomic number: E

and Z used to describe position of the two highest priority atoms.

Stereogenic Atoms

● The two C atoms in C=C when cis and trans isomers are possible are stereogenic atoms.

● Other possibilities for stereogenic atoms.The C in CHFClBr is stereogenic.

Stereogenic Atoms

● Any tetrahedral C with 4 different atoms attached will be stereogenic.

Stereogenic Atoms

● Stereoisomers may be mirror images of each other: enantiomers.

If the mirror images are not superposable, the stereoisomers are chiral.

Figure 16.12

Stereogenic Atoms

…or they may not be mirror images of each other: diastereomers.

cis and trans isomers are diastereomers.

Optical Activity

● Optically active compoundsRotate the plane of polarized light.

● Specific rotation is a measure of the ability of a compound to do this.

Optical Activity

● Need a method for distinguishing the left handed and right handed version of a chiral center in a molecule or ion.

As before, substituents are prioritized.

R and S used to designate the two possible orientations of substituents.