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118 Cards in this Set
- Front
- Back
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functional group
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collection of atoms at a site that have characteristic behavior in all molecules where it occurs
-reacts in a typical way, generally independent of the rest of the molecule |
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Alkenes
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C-C double bond
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Alkynes
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C-C triple bond
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Arenes
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have special bonds that are represented as alternating single and double C-C bonds in a sex membered ring
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Carbonyl groups
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groups with a carbon-oxygen double bond
-aldehyde, ketone, carboxylic acid, ester, thioester, amide, acid chloride |
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Alkanes
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compounds with C-C single bonds and C-H bonds only (no functional groups)
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the formula for an alkane with no rings in it must be
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CnH(2n+2) where n=number of C's
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Alkanes are _____ with hydrogen
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saturated (no more can be added)
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Alkanes are also called
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aliphatic compounds
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isomers
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different compounds with same molecular formula
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two types of isomers
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Constitutional Isomers
Stereoisomers |
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Constitutional isomers
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compounds that have the same molecular formula, differ in the way the atoms are connected to each other
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straight chain alkanes are named according to...
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the number of carbon atoms they contain
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the suffix ____ is added to the end name
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-ane
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methane
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CH4
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Ethane
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C2H6
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Propane
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C3H8
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Butane
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C4H10
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Pentane
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C5H12
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Hexane
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C6H14
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Heptane
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C7H16
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Octane
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C8H18
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Nonane
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C9H20
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Decane
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C10H22
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alkyl group
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remove one H from an alkane (a part of a structure)
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Naming an alkyl group
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replace -ane ending of alkane with -yl ending
-ex. CH3 is methyl -CH2CH3 is ethyl |
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Primary Carbon
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bonded to one other carbon
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Secondary carbon
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bonded to two other carbons
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Tertiary carbon
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bonded to three other carbons
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Quaternary carbon
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bonded to four other carbons
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IUPAC nomenclature
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prefix-locant-parent-suffix
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steps in naming alkanes
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1. find parent hydrocarbon chain
2. number atoms in main chain 3. identify and number the substituents 4. write the name as a single word 5. name a complex substituent as though it were itself a compound |
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finding parent hydrocarbon chain
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-find longest continuous chain of carbon atoms
-if two different chains of equal length are present, choose the one with the larger number of branch points as the parent |
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numbering atoms in main chain
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-beginning at end nearer the first branch point, number each carbon atom in the parent chain
-if there is branching an equal distance away from both ends of the parent chain, begin numbering at the end nearer the second branch point. |
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identifying substituents
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-assign a number, called a locant, to each substituent to locate its point of attachment to the parent chain
-if there are two substituents on the same carbon, give both the same number. |
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writing name as a single word
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-use hyphens to separate the different prefixes
-use commas to separate numbers -if two or more identical substituents are present, use on of the multiplier prefixes (di-, tri-, tetra-, etc.) |
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naming complex substituent
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begin numbering the branched substituent at its point of attachment to the main chain.
-place the complex substituent name within parentheses when naming the entire molecule |
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ethane conformations
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-stereochemistry concerned with 3D aspects of molecules
-sigma bonds are cylindrically symmetrical -rotation is possible around C-C bonds in open-chain molecules |
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Conformations
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molecules with different spatial arrangement of atoms as a result of rotation about single bonds.
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conformations can be represented in two ways
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sawhorse representation; and newman projection
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Staggered
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most stable; all 6 C-H bonds are as far away as possible
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Eclipsed
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least stable; all 6 C-H bonds are as close as possible to each other
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Torsional Strain
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An increase in the energy of a molecule caused by eclipsing interactions between groups attached to adjacent carbon atoms
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Torsional strain arises from
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repulsion of eclipsing bond electron pairs
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the eclipsed conformation of propane has 3 interactions:
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two ethane-type H-H interactions, and one H-CH3 interaction
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Steric Strain
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repulsive interaction occurring between atoms that are forced closer together than their atomic radii allow
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conformational situation is ____ complex for larger alkanes
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more
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not all staggered conformations has the same ____, and not all eclipsed conformations have the same _____
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energy
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Anti conformation
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methyl groups are 180* apart
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Guache conformation
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methyl groups are 60* apart
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organic chemistry
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the chemistry of compounds that contain carbon
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why is carbon special?
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carbon can bond to other atoms in many different ways, and carbon can bond to other carbon atoms
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isotopes
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atoms of the same element that have different numbers of neutrons and therefore different mass numbers
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electron configuration of an atom
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its lowest energy electron arrangement
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Aufbau principle
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lowest energy orbitals fill up first
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Pauli exclusion principle
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only two electrons can occupy an orbital, and they must be of opposite spin
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Hund's rule
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if two or more empty orbitals of equal energy are available, electrons occupy each with spins parallel until all orbitals have one electron
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periodic table of elements: period is determined by
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the total number of electron shells an atom has
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why do atoms form bonds?
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stability
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ionic bonds
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transfer of electrons
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covalent bond
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sharing of electrons
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lewis structures
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show valence electrons of atoms atoms as dots
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carbon forms
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four bonds
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Nitrogen forms
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3 bonds
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Oxygen forms
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2 bonds
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Kekule structure (line bond structure)
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a two electron covalent bond is indicated by a line drawn between atoms
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two models have been developed to describe covalent bonding
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-valence bond theory
-molecular orbital theory |
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valence bond theory
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covalent bond forms when two atoms approach each other closely so that a singly occupied orbital on one atom overlaps a singly occupied orbital on the other atom
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bond length
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distance between nuclei that leads to maximum stability
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hybridization is
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the combination of two or more atomic orbitals to form the same number of hybrid atomic orbitals, each having the same shape and energy
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sp3 hybrid orbitals
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s orbital and three p orbitals combine to form four equivalent, unsymmetrical, tetrahedral orbitals
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pi bonds are formed by
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unhybridized p orbitals
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sp3
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tetrahedral; 109.5*
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sp2
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3 attachments; trigonal planar; 120*
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sp
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2 attachments; linear; 180*
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molecular orbital theory
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describes covalent bond formation as arising from a combination of atomic orbitals on different atoms to form molecular orbitals
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molecular orbital
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where electrons are most likely to be found (specific energy and general shape) in a molecule
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additive combination (bonding) is ____ in energy
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lower
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subtractive combination (antibonding) is ____ in energy
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higher
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polar covalent bonds
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bonding electrons are attracted more strongly by one atoms than by the other;
electron distribution between atoms is not symmetrical |
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bond polarity is due to
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differences in electronegativity
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electronegativity
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intrinsic ability of an atom to attract the shared electrons in a covalent bond
-the higher the electronegativity number, the more an atom attracts electrons towards it |
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the attraction that a bonding pair of electrons feels for a particular nucleus depends on
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-the distance from the nucleus
-the number of protons in the nucleus |
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electronegativity patterns on periodic table
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-increases across a period (row) as the nuclear charge increases
-decreases down a group (column) as the atomic radius increases |
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nonpolar covalent bonds
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difference in EN less than .5
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polar covalent bonds
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difference in EN between .5-2
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Ionic bonds
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difference in EN greater than 2
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inductive effect
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the shifting of electrons in a sigma bond in response to the electronegativity of nearby atoms
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Dipole moments
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-molecular polarity; results from the vector summation of all individual bond polarities in the molecule.
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dipole moment is measured in
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debyes (D)
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formal charges
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charges that are assigned to specific atoms within a molecule
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formal charge=
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(number of valence electrons in free atom) - (number of bonding electrons/2) - (number of nonbonding electrons)
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Resonance
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-some molecules have structures that cannot be shown with a single representation
-in these cases we draw structures that contribute to the final structure but which differ in the position of the pi bond(s) or lone pair(s) |
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resonance hybrid
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-a structure with resonance forms is a hybrid of the two forms
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resonance forms differ only in
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the placement of their pi or nonbonding electrons
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how to connect resonance structures
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use a double headed arrow (NOT A DOUBLE ARROW)
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if the structures differ in the POSITION of atoms, they are
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isomers, not resonance structures
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when two resonance forms are nonequivalent, the actual structure of the resonance hybrid is closer to
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the more stable form
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the larger the number of resonance forms,
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the more stable a substance is
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Bronsted acid
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a substance that donate a hydrogen ion
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Bronsted base
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a substance that accepts the hydrogen ion
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conjugate base
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the ion or molecule remaining after the acid has lost a proton
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conjugate acid
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the species created when the base accepts the proton
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Keq
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the equilibrium constant; a measure related to the strength of the acid
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stronger acids have
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larger Keq
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Ka
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the acidity constant; ranges from 10^15 for strongest acids to (10^-60) for the weakest
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pKa=
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-logKa
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smaller value of pKa indicates
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a stronger acid
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organic acids
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characterized by the presence of positively polarized hydrogen atom
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two major categories of organic acids
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1. those that lose a proton from O-H, such as methanol and acetic acid
2. those that lose a proton from C-H, usually from a carbon atoms next to a C=O double bond (O=C-C-H) |
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organic bases
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have an atom with a lone pair of electrons that can bond to H
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most common organic bases
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Nitrogen containing compounds
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Oxygen containing compounds can
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react as bases when with a strong acid or as acids with strong bases
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Lewis acids
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electron pair acceptors
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Lewis bases
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electron pair donors
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curved arrow
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means that a pair of electrons moves from the atom at the tail of the arrow to the atom at the head of the arrow
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most oxygen and nitrogen containing organic compounds are Lewis bases because
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they have lone pairs of electrons
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some lewis bases, such as carboxylic acids, esters, and amides have
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more than one atom with a lone pair
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