Ch. 11: Carbon A Multifarious Element

Why Carbon?

• • • Versatility Single, double, triple bonds Structural diversity

Short-hand for expressing carbon based compounds • • • • C 4 H 10 : butane Structural formula Condensed structural formula Carbon skeleton formula • • C 4 H 8 C 4 H 6

Isomers

• • Isomers – same composition, diff. structures Structural isomers: same # atoms, diff. structures Ethanol (C 2 H 6 O) vs. dimethylether (C 2 H 6 O)

Problems

• Draw all isomers of C 3 H 8 O. There are 3.

• Draw all isomers of C 4 H 8 Br 2 . There are 9.

Stereoisomers

• • • • Same formula, diff. orientation Two types: 1) geometric 2) optical isomers

Geometric isomers

• •

Require double bond!

Cis vs. trans

Optical isomers

• • • Nonsuperimposable mirror images Called chiral molecules (chirality) Pairs of chiral molecules = enantiomers

Classes of Carbon-Containing Cmpds • • • • • • Hydrocarbons Only C & H Alkane: C n H 2n+2 (Saturated every C-C bond single) Alkene: C n H 2n (at least one double bond btwn C’s) (Unsaturated  double, triple bonds)

Classes of Carbon-Containing Cmpds • • • Alkyne: C n H 2n-2 btwn C’s) (at least one triple bond Cyclohydrocarbons: rings of carbon Aromatic: rings w/pi-bonding – benzene

Naming Alkanes

• • • Suffix: -ane Count out longest carbon chain Prefixes: • • • • • • • • • • 1C meth 2C eth 3C prop 4C but 5C pent 6C hex 7C hept 8C oct 9C non 10C dec-

Naming Alkanes

• • Hydrocarbon substitution = alkyl groups Meth  methyl, etc.

• Use number, followed by “-”, to designate placement of substituent – 2-methylpentane • If 2 or more of same subs.  – 2,3-dimethylpentane di, tri, tetra, etc.

• If more than one different alkyl group, use alphabetic ordering – Butyl precede ethyl precedes methyl • 4-ethyl-3-methylheptane •

In naming hydrocarbons always go with longest carbon-chain

Draw out the following alkanes and rename them, if needed • • • • • Hexane 2-methylhexane 2,2-diethylpropane 4-ethyl-2-methylnonane Now, I’ll draw some and you name them

Naming Alkenes, alkynes

• • Start counting carbon chain from lowest carbon containing double/triple bond 1-propene, not 2-propene • Use number, followed by “-”, to designate placement of double or triple bond – 1-butene – 2-octyne

• • • • Draw the following and if there is isomerism draw both structures and name them • 1-hexene 2-hexene 3-heptyne 2-methyl-3-heptyne Now, I’ll draw some and you name them

Naming Halohydrocarbons

• Same rules apply – In alphabetical order – Bromine  bromo – chlorine  – fluorine  – iodine  chloro fluoro iodo • Ex: 2-chlorobutane • • • • Practice (fix if necessary): 3-bromo-2-chloropentane 3,3-diiodobutane Now, I’ll draw some and you name them

Naming Aromatic Cmpds

• • • • • Monosubstitution: – Methylbenzene  – Phenol – Aniline Disubstitution: o - = ortho m - = meta p - = para toluene

Practice

• • Chlorobenzene (does it make a difference where you put the Cl?) Draw all isomers (and name them) of a benzene that has 1 bromine and one fluorine – Which combinations are disallowed and why?

Other functional groups

• • • • • Functional group = characteristic grouping or arrangement of atoms Alcohols = R-OH Methan ol , ethan ol , propan ol , etc.

Structural isomers of alcohols 1,2-ethanediol = ethylene glycol

Practice: rename if necessary

• • • • 1-propanol 2-propanol 3-propanol Now, I’ll draw some and you name them

Other functional groups

• Ether: ROR’ 1) Select the longest carbon chain and name it as the correct alkane.

2) Change the “-yl” ending of the other (shorter) hydrocarbon group to “-oxy” to obtain the alkoxy group name.

3) Combine the two names giving the alkoxy group name first.

Practice

• • • • Dimethylether Butoxyhexane methoxyethane Now, I’ll draw some and you name them

Other functional groups

• • • • Amines RNH 2 Putrescine = 1,4-butanediamine Cadaverine = 1,5-pentanediamine

Practice

• • • Triethylamine Triisopropylamine Now, I’ll draw some and you name them

Other functional groups

• • • • Aldehydes RCOH Start counting the carbon-chain from the C=O Methan al , butan al , hexan al • • • • Ketones RCOR’ Start counting the carbon-chain from the C=O 2-propan one , 3-heptan one

Practice

• • • • • Methanal Hexanal 2-pentanone 4-decanone Now, I’ll draw some and you name them

Other functional groups

• • • • Carboxylic acids RCOOH Start counting the carbon-chain from the C=O Methanoic acid, ethanoic acid, etc.

• • • • • • • Esters RCOOR’ Start counting the carbon-chain from the C=O -OR’  RCO  takes on alkyl name takes on –oate suffix Thus, HCOOCH 3  methyl methanoate By the way, acetate = ethanoate

Practice

• • • • • Hexanoic acid 2-methylpropanoic acid (give its other name) Hexyl ethanoate Butyl butanoate 3-methylbutyl ethanoate (has a more common name) • Now, I’ll draw some and you name them

Other functional groups

• • • Amides RCONR 2 Ex: methanamide, ethanamide

Polymers

• • • • Huge molecules with repeating monomers (subunits) Thermoplastics (polyethylene, styrofoam): respond to heating Soften and flow when heated, harden when cooled; reversible – Over 60 million tons of polyethylene produced annually!

Thermosetting plastics (Formica-brand): initially soft, but solid when heated; irreversible

Styrofoam, Teflon, silicone, Kevlar

Condensation Polymers

• • Combining monomers and splitting out small molecules (like water) – Demo • Making nylon Demo – Green “snot”

Green “snot”

Copolymers

• • Polymerization of 2 (or more) diff. monomers Such as: – Styrene-butadiene rubber (SBR) • Predominately used for car and light-truck tires