Chapters 3/4 Vocabulary Terms

Aliphatic

A non aromatic hydrocarbon such as a simple alkane, alkene, or alkyne

Alkane

A class of compounds of carbon and hydrogen that contains only single bonds

Alkyl halide

A compound with a halogen atom bonded to a saturated, hybridized carbon atom

Anti conformation

The geometric arrangement around a carbon-carbon single bond in which the two largest substituents are 180^o apart as viewed in a Newman projection

Branched-chain alkane

Alkanes that contain a branching connection of carbons

carbonyl group

The C double bond to O functional group

conformation

The three-dimensional shape of a molecule at any given instant, assuming that rotation around single bonds is frozen

conformational isomer

molecules with the same atomic connectivity that differ in their spatial arrangement due to rotation around single bonds

conformers

conformational isomers

constitutional isomer

Isomers that have their atoms connected in a different order

eclipsed conformation

The geometric arrangement around a carbon — carbon single ond in which the bonds to substituents on one carbon are parallel to the bonds to substituents on the neighboring carbon

functional group

An atom or group of atoms that is part of a larger molecule that has a characteristic chemical reactivity

gauche conformation

The conformation of butane in which the two methyl groups lie 60^o apart as viewed in a Newman projections, has a 3.8kJ/mol steric strain

hydrocarbon

A class of compounds that contain only carbon and hydrogen

isomer

Compounds that have the same molecular formula but different structures

Newman projection

A means of indicating stereochemical relationships between substituent groups on neighboring carbons. The carbon — carbon bond is viewed end-on, and the carbons are indicated by a circle. Bonds radiating from the center of the circle are attached to the front carbon, and bonds radiating from the edge of the circle are attached to the rear carbon

R group

A generalized abbreviation for an organic partial structure

saturated

A molecule that has only single bonds and thus can’t undergo addition reactions

sawhorse representation

A manner of representing stereochemistry that uses a stick drawing and gives a perspective view of the conformation around a single bond

staggered conformation

The three-dimensional arrangement of atoms around a carbon — carbon single bond in which the bonds on one carbon bisect the bond angles on the second carbon as viewed end-on

stereochemistry

The branch of chemistry concerned with the three-dimensional arrangement of atoms in molecules

steric strain

The streain imposed on a molecule when two groups are too close together and try to occupy the same space

straight-chain alkane

Alkanes whose carbon atoms are connected without branching

substituent

an atom or group of atoms taking the place of another atom or group occupying a specified position in a molecule

torsional strain

The strain in a molecule caused by electron repulsion between eclipsed bonds

alicyclic

A non-aromatic cyclic hydrocarbon such as a cycloalkane or cycloalkene

angle strain

The strain introduced into a molecule when a bond angle is deformed from its ideal value, in small ring cycloalkanes, it results from compression of ond angles to less than their ideal tetrahedral values

axial position (cyclohexane)

Bonds or positions in chair cyclohexane that lie along the ring axis, perpendicular to the rough plane of the ring

boat cyclohexane

a conformation of cyclohexane that bears a slight resemblance to a boat, this cyclohexane has no angle strain but has a large number of eclipsing interactions that make it less stable than chair cyclohexane

bridgehead atom

An atoms that is shared by more than one ring in a polycyclic molecule

chair conformation

A three-dimensional conformation of cyclohexane that resembles the rough shape of a chair, is the lowest-energy conformation of the molecule

cis-trans isomers

Stereoisomers that differ in their stereochemistry about a ring or double bond

conformational analysis

A means of assessing the energy of a substituted cycloalkane by totaling the steric interactions present in the molecule

cycloalkanes

An alkane that contains a ring of carbons

1,3-diaxial interaction

The strain energy caused by a steric interaction between axial groups three carbon atoms apart in chair cyclohexane

equatorial position (cyclohexane)

Bonds or positions in chair cyclohexane that lie along the rough equator of the ring

polycyclic molecule

A molecule containing more than one carbon ring

ring-flip (cyclohexane)

A molecular motion that interconverts two chair conformation of cyclohexane, the effect is to convert an axial substituent into an equatorial substituent

stereoisomer

Isomers that have their atoms connected in the same order but have different three-dimensional arrangements, includes enantiomers and diastereomers

twist-boat conformation

A conformation of cyclohexane that is somewhat more stable than a pure boat conformation