Chapter 24

Structural Isomers

same molecular formula, but different bond connectivities (straight chain vs. branched alkanes

functional group

an atom or a group of atoms that imparts characteristic physical and chemical properties in a molecule

Naming Alkanes

1. The suffix "ane" identifies a molecule as an alkane 2. CH4= methane C2H6= ethane C3H8= propane etc.

Naming Alkenes

1. find longest carbon chain with double bond inside 2.number the carbon containing the double bond lower than the substituents

Naming alkanes Steps

1. name the longest continuous chain 2. number the longest chain starting at the end nearest to subsitiuent 3. name each sutstituent (alkyl group) and indicated the number of the carbon to which it is attached. 4. use di, tri, tetra.. if two or more alkyl groups are identical. 5. list alkyl groups in alphabetical order Example: 1. six= hexane 2. number left to right 3. 2-methyl and 4-methyl 4.2,4-dimethylhexane

Naming organic molecules

1. suffix: which family the molecule belongs to 2. root/base/parent: number of carbons in longest chain 3. Prefix: location and name of substituents

what three main features characterize organic chemicals

1. their carbon skeleton 2. their functional groups 3. structural complexity, chemical diversity

Reactions of alkanes

Alkanes are rather unreactive due to the presence of only C-C and C-H sigma bonds. Make great non polar solvents -undergo combustion reactions

Four Families of Hydrocarbons

Alkanes, alkenes, alkynes, and aromatics

Haloalkanes (R-X)

Alkyl halides are organic molecules containing a halogen atom bonded to an sp3 hybridized carbon of an alkyl group

How are Carbon atoms classified

Based on the number of other carbons directly bond to them. Primary carbon (1 degree) - bonded to one other C atom. Secondary carbon- bonded to two other C atoms. Tertiary carbon - bonded to three four C atoms. Quaternary carbon - bonded to four other C atoms

Acyclic Alkenes

Contain at least one double bond, no rings, generic molecular formula = CnH2n (one double bond), additional double bonds reduces the H number by 2. They are unsaturated hydrocarbons example: C2H4 Same as cyclic alkanes

Acyclic Alkanes

Contain only C and H in single covalent bonds, no rings, all carbons spy hybridized (tetrahedral), general formula CnH2n+2, also known as saturated hydrocarbons. example: CH4, C2H6

Rotation

Rotation about single bonds is relatively unhindered in acyclic alkanes but not in cyclic alkanes

how to identify chiral molecules

a carbon atom bonded to four different groups.

alkyl group

carbon substituents bonded to a long carbon chain. Is formed by removing one H atom from an alkane. change the -ane to -yl example: methane becomes methyl

Organic Chemistry

carbon-containing compounds

Geometric isomers of Acyclic Alkenes

cis: two on the same side of the double rings trans: two on opposites sides of the double rings

alkenes

contain at lease one double bond

cyclic alkenes (cycloalkenes)

contain at least one ring with double bond, generic molecular formula = CnH2n-2. additional double bonds or rings reduce number of H# by 2. example: C6H10

alkynes

contain at least one triple bond

acyclic alkynes

contain at least one triple bond but no rings, generic formula = CnH2n-2. additional triple rings reduce the H number by 4. Unsaturated hydrocarbons example: C4H6

cyclic alkanes (cycloalkanes)

contain only C and H in single covalent bonds; at least ONE ring, all carbons spy hybridized, general formula CnH2nc, five and six membered rings are most stable. Example: C6H12

alkanes

contain only single covalent bonds

aromatics

contain rings with delocalized electrons

Aromatic hydrocarbons

hydrocarbon consisting of one or more planar rings that exhibit extensive delocalized multiple bonding; 6-membered rings most common. Most common aromatic compound: Benzene C6H6 very stable because of delocalized electrons

concatenation

linking as in a chain

Chiral

not superimposable on its mirror image, no plane of symmetry

Derivatives of Benzene

o= ortho = 1,2 disubstituted m= meta = 1,3 disubstituted p = para = 1,4 disubstituted

enantiomers

pair of stereoisomers that are mirror images of each other. also called optical isomers since that interact with the plane polarized light in different ways.

Properties of Hydrocarbons -physical -chemical

physical: generally non-polar, soluble in organic solvents, insoluble in water, boiling point and melting point increase with chain length due to increased intermolecular Chemical: alkanes relatively unreactive, -alkenes, alkynes, and benzene more reactive (due to double and triple bonds)

Geometric isomers of cycloalkanes

restricts rotation. but still can have cis and trans

Geometric isomers

result from restricted rotation around bonds. Have the same molecular formula and bond connectivity but differ from each other in a spatial arrangement of groups

optical isomers

stereoisomers having non-superimposable mirror image

Stereochemistry

the study of spatial arrangements of atoms in molecules and the effects of these arrangements on the chemical and physical properties of substances