organic chem 1 - basics

organic compounds contain:

• Carbon

• Hydrogen

• Oxygen

• Nitrogen

multiple bonding and substituents can

• Different atoms/group of atoms can be placed on carbons

• Basic atoms is hydrogen but groups contain oxygen, nitrogen, halogens and sulphur are common

• Chemistry of organic compound is determined by functional group

molecular formula

exact no. of atoms of each element present in molecule

empirical formula

simplest whole number ratio of atoms in molecule

structural formula

 minimal detail using conventional groups

displayed formula

shows bonds

skeletal formula

removes H atoms leaving carbon skeleton

general formula

represents any member of a homologous series

alkanes

CnH2n

only C and H

all single bonds

alkenes

only C and H

C=C

alcohols

only one O

has O-H group

can classify as 1o, 2o, 3o according to position of O-H group on carbon skeleton

aldehydes

only one O

has C=O

C=O is at end of chain so next door is H atom

ketones

only one O

has C=O

C=O group isnt at end of chain

carboxylic acids

has 2 O

has O-H and C=O on same carbon

-COOH has to be at end of chain

esters

has 2 O

one O is part of C=O bond

ethers

has 1 O

O is sandwiched between two carbon atoms

amines

1 N

has N-H group

Classified as 1o/2o/3o according to position of N-H group on carbon skeleton

amide

1 N and 1 O

One O is part of C=O and nitrogen is next door

nitrile

Has 1N

Has C-N triple bond

thiols

Has 1 S

Has H-S bond

e.g. methanethiol

haloalkanes

Contains carbon halogen bonds

e.g. F, Cl, Br, I

classified according to environment of halogen

isomerism in haloalkanes

chains and rings

Carbon can be arranged in straight chains or branched chains or rings

naming

Trivial: based on some property or historical aspect; the name tells you little about structure

Systematic: based on agreed set of rules IUPAC; exact structure can be found from name

e.g. acetone-propanone  acetic acid - ethanoic acid

IUPAC nomenclature

• Stem and suffix

• Stem - how many carbons in longest chain

• Suffix - functional group

how long is chain

Single covalent bonds free to rotate

suffix

-ane

-ene

-ol

-al

-one

-oic acid

In many cases position of functional group must be given to avoid any ambiguity

 

naming alkanes

alkanes

isomerism

structural

• Chain - diff arrangements of carbon skeleton , more branching = lower BP

• Positional - same carbon chain, functional group diff place

• Functional group - diff functional group, same formula

geometric isomerism

geometric isomerism

how to tell if isomerism exists

isomerism in butene

3 structural isomers only one shows geometric isomerism

But-1-ene

Cis but-2-ene

Trans but-2-ene

2-methylpropene

 

E-Z Isomerism

E- opposite

Z- same side

optical isomerism

stereochemistry

functional groups

polarity of bonds

Most functional groups (except for alkenes, alkynes and phenyl)

Electronegativity difference C to H is very small, thus electron density is nearly uniform around alkane C-H bond

Presence of extra pi bonds between two C s make C-C region slightly delta negative

polarity of bonds

inductive effects