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