1. Chapter 24: Organic chemistry
Chemistry 1062: Principles of Chemistry II
Andy Aspaas, Instructor

2. Carbon
Carbon: central element of organic chemistry
Organic compounds: compounds containing carbon-carbon bonds
4 valence electrons: 4 must be shared from other atoms
4 single bonds (tetrahedral)
1 double bond, 2 single bonds (trigonal planar)
2 double bonds (linear)
1 triple bond, 1 single bond (linear)

3. Hydrocarbons
Hydrocarbon: molecule that contains only carbon and hydrogen atoms
Saturated hydrocarbons: only C–C single bonds
May be cyclic or acyclic
Unsaturated hydrocarbons: contain some carbon-carbon double and/or triple bonds
Aromatic hydrocarbons: contain benzene rings
(Non-aromatic hydrocarbons are aliphatic)

4. Alkanes and cycloalkanes
Alkanes are acyclic saturated hydrocarbons
Cycloalkanes are cyclic saturated hydrocarbons
Molecular formula: indicates only type and quantity of atoms in a molecule
Structural formula: indicates connectivity in the molecule (which atoms are bonded to which)
Structural formulas look like Lewis structures
Condensed structural formulas don’t draw the bonds, but still indicate connectivity

5. Straight-chain alkanes
Straight-chain alkanes (or normal alkanes) have all carbons in a row
n- at beginning indicates straight-chain (normal)
General formula: CnH2n+2
Name
Molecular formula
Structural formula
Methane
CH4
Ethane
C2H6
CH3CH3
Propane
C3H8
CH3CH2CH3
n-Butane
C4H10
CH3(CH2)2CH3

6. Straight-chain alkanes (5 C through 10 C)
For straight-chain alkanes 5 C through 10 C, use Greek prefix followed by -ane
Name
Molecular formula
Structural formula
n-pentane
C5H12
CH3(CH2)3CH3
n-hexane
C6H14
CH3(CH2)4CH3
n-heptane
C7H16
CH3(CH2)5CH3
n-octane
C8H18
CH3(CH2)6CH3
n-nonane
C9H20
CH3(CH2)7CH3
n-decane
C10H22
CH3(CH2)8CH3

7. Isomerism in alkanes
n-Butane has a contsitutional isomer (same number and kind atoms, different bonds)
Same molecular formula, different structural formula
Isobutane: branched, all carbons not in a row
CH3(CH3)CHCH3 (parentheses mean group is not in the main chain)

8. Branched alkanes
More complex branched alkanes require different naming rules
Any of the straight-chain alkanes can be made into “substitutents” - or branches off a main chain
Methane becomes methyl as a branch (—CH3)
Ethane becomes ethyl as a branch (—CH2CH3), etc

9. Naming complex branched alkanes
Start by identifying the longest carbon chain
Identify branches off the longest chain as their substituent name (methyl, ethyl, propyl, etc)
Number longest chain starting at end closest to the first branch
Name the compound, starting with branches and indicating the number on the main chain to which the branch is attached

10. Cycloalkanes Saturated hydrocarbons which form a ring of carbon atoms
General formula CnH2n
Prefix name with cyclo- and name as if straight chain
E.g. cyclobutane (4 carbons); cyclohexane (6 carbons)
Any organic molecule can be drawn as a line-angle formula, where carbons and hydrogens are not explicitly shown.
Line-angle drawing of cyclohexane is simply a hexagon
Practice drawing!

11. Alkenes and alkynes
Alkenes and alkynes: unsaturated hydrocarbons
Typically more reactive than alkanes (reactions can occur at carbon-carbon double and triple bonds)
Hydrogenation: addition of two hydrogen atoms across a double bond
Alkenes: general formula CnH2n just like cycloalkanes
Names end with -ene (compared to -ane ending of alkanes)

12. Naming alkenes and alkynes
Ethene is the simplest alkene (CH2=CH2)
Common name is “ethylene”
When there are more than one possible place to put the double bond, it’s location must be indicated
Start numbering carbons at end closest to the double bond, and indicate the lower-numbered carbon involved in double bond
Ex. 1-butene: CH2=CH–CH2–CH3
2-butene: CH3–CH=CH–CH3
Alkynes are named the same way, with -yne instead of -ene

13. Aromatic hydrocarbons
Benzene ring: six-membered carbon ring with alternating single- and double-bonds

14. Nomenclature of aromatic hydrocarbons
For singly substitued benzenes, use substituent names and benzene as the suffix (ex. Methylbenzene, ethylbenzene, etc.)
When 2 identical groups are substituted on a benzene, ortho-, meta-, and para- are used to differentiate the isomers
Multiple substituents require the benzene ring to be numbered from 1-6 so that the substitutents get the smallest possible numbers

15. Hydrocarbon derivatives
Most organic molecules contain elements other than carbon and hydrogen
Heteroatom: atom that’s not C or H in an organic molecule
Functional group: common grouping of atoms which reacts in a particular way
Oxygen-containing functional groups are the most common

16. Oxygen-containing functional groups
Molecule fragments which symbolize oxygen-containing functional groups
R and R’: symbols for general hydrocarbon groups
Alcohol
Aldehyde
Ether
Ester
Ketone
Carboxylic acid

17. Alcohols
Alcohol: R–OH functional group
Named with similar rules to hydrocarbons
Main chain must contain carbon bonded to –OH
Suffix -ol on chain name
Position of –OH group indicated by number (omit if unnecessary)
Ex. Methanol, ethanol, 2-propanol

18. Ethers
Ether: R–O–R’
Common name: list the two R groups and suffix with “ether”
Ex. Methyl ethyl ether, diethyl ether
IUPAC name: alkoxy derivative of longer chain
Ex. Methoxy ethane, ethoxy ethane
Diethyl ether (or just ‘ether’) used as solvent, previously an anesthetic

19. Aldehydes
Aldehydes, ketones, carboxylic acids, and esters all contain a carbonyl group (C=O double bond)
Aldehyde: carbonyl with a hydrogen attached
Usually abbreviated –CHO
Methanal: CH2O (common name: formaldehyde)
Ethanal: CH3CHO (common name: acetaldehyde)

20. Ketones
Ketone: carbonyl with two hydrocarbon groups attached
Abbreviated –CO–
Named with -one suffix on stem name, number indication position of carbonyl
Propanone: CH3COCH3 (common name: acetone)
2-butanone: CH3COCH2CH3 (common name: methyl ethyl ketone)

21. Carboxylic acids
Carboxylic acids contain a carboxyl group, –COOH
Named like aldehydes, but with ‘-oic acid’ as suffix
Many have common names
CH3COOH: ethanoic acid - vinegar (common name: acetic acid)
CH3(CH2)2COOH: butanoic acid - rancid dairy (common name: butyric acid)

22. Esters
Ester: RCOOR’
Formed by reaction of alcohol with carboxylic acid
Ex. Ethanol + Acetic acid  Ethyl acetate
Pleasant, fragrant smells
Many familiar fruit smells are esters

23. Nitrogen-containing functional groups
Amine: RnNH3-n
Generally sharp- or strong-smelling
Ammonia: NH3
Triethylamine (CH3CH2)3N smells like dead fish

24. Amides
Amides: RCONH2 or RCONHR’
Formed by reaction of amine with carboxylic acid, similar to ester formation