Structure 3.2 - functional groups, cis-trans isomerism, enantiomers, mass spectra, IR spectra, and H NMR spectra

alkene

alkane

alkyne

aldehyde

ketone

alcohol

Ether

carboxylic acid

amine

amide

arene (phenyl)

Functional group

a group of atoms within a molecule that is responsible for the characteristic chemical reactions of the molecule.

homologous series

a series of organic compounds of the same family that differ by a CH2 group.

characteristics of homologous series

• similar chemical properties and show a gradation in physical properties

• same general formula

• same functional group

compounds that have hydrogen bonds

alcohols, amines, amides, carboxylic acids

compounds that have dipole-dipole

aldehydes, ketones, and esters

compounds that have LDFs

alkanes, alkenes, alkynes

cis-trans isomerism

When there is a restriction on the rotations that can occur around a bond because there is a double bond or there is a ring structure in a cyclic compound.

Cis isomer

An isomer that has the same groups on the same side of the carbon-carbon double bond.

Trans isomer

An isomer that has the same groups on opposite sides of the carbon-carbon double bond.

Chiral compound

A compound that has a carbon that is attached to four different functional groups.

Enantiomer

The two possible 3-D configurations of the chiral compounds which are mirror images and are non-superimposable.

Characteristics of enantiomers

• rotate the plane of polarized light by the same amount but in different directions

• they have the same physical properties

• the same chemical properties

  • except in the case where they are reacting with other chiral compounds

Optically active

A term used to describe the observation that two enantiomers do indeed rotate light in different directions.

Racemix mixture

A mixture that contains equal amounts of two enantiomers.

IR spectroscopy

Used to determine the type of bond that is present in a molecule.

What happens when molecules absorb energy from the IR region?

The bonds between the atoms begin to vibrate (they stretch and bend).

What type of molecules have IR interactions

Polar molecules.

wavenumber

The frequency of IR radiation absorbed by a bond.

H NMR spectroscopy

Gives information on the different chemical environments of hydrogen atoms in a molecule (where they are located throughout the molecule).

chemical shift

The position of the NMR signals relative to the TMS standard position.