ochem test 1

Anhydride

Ether

Aldehyde

Ketone

Sulfide

Amine

Thiol

Ester

Aromatic/Arene

Acyl Halide

Alkyne

Amide

Alkane

Alkyl Halide

Alchohol

Carboxylic Acid

Alkene

Allylic lone pair

Allylic cation

Lone pair e- adjacent to a carbocation

polar pi bond

benzene group

determining the most significant resonance form: 3 things to look for (most important to least important)

1. greatest number of atoms with complete octet

2. structure with fewer nonzero formal charges is more stable

3. if all other things are equal → better to have negative charge on the more electronegative atom

localized lone pairs

not used in resonance

delocalized lone pair

can be used in resonance

constitutional isomers

same chemical formula, different connectivity of atoms

tips for drawing constitutional isomers

1. start with the carbons and how many ways you can arrange (the skeleton/backbone)

2. fill in the hydrogens

3. give each atom a complete octet

ionic bonds

held together by electronegativity

covalent bonds

sharing of electrons

most common bond between 2 nonmetals

exceptions to the octet rule (1)

elements such as B and Al form compounds with fewer than 8 valence electrons

ex: BH3

exceptions to octet rule (2)

elements in the third period can form molecules with more than 8 valence electrons

ex: ICl3

formula for formal charge

number of valence electrons (periodic table) - number of electrons in lone pairs - ½ bonding electrons

formal charge of 4 bonds to carbon

0

formal charge of 3 bonds to carbon and 1 lone pair

-1

formal charge of 3 bonds to carbon and no lone pairs

+1

formal charge of 2 bonds to oxygen and 2 lone pairs

0

formal charge of 1 bond to oxygen and 3 lone pairs

-1

formal charge of 3 bonds to oxygen and one lone pair

+1

formal charge of 3 bonds to nitrogen and one lone pair

0

formal charge of 2 bonds to nitrogen and 2 lone pairs

-1

formal charge of 4 bonds to nitrogen

+1

how does electronegativity change across the periodic table

increases up and to the right

covalent bonds examples

C-C, C-H

small difference in electronegativity

polar covalent bond electronegativity difference

difference of 0.5-1.7

ex: N-H, C-O, Li-C

ionic bond electronegativity difference

greater than 1.7

Hunds rule

each orbital must be occupied by one electron before electrons are paired

node

zero probability of finding an electron

molecular orbital theory

linear combination of atomic orbitals

difference between atomic orbitals and molecular orbitals

atomic- associated with individual atoms

molecular- associated with the entire molecule

sigma bond

direct overlap of orbitals

pi bonds

parallel overlap of orbitals, not as strong as sigma bonds

how to determine highest boiling point

strongest IMFs

IMFs from strongest to weakest

1. hydrogen

2. dipole dipole

3. london dispersion

how to determine the highest boiling point from line structures

1. the longer the carbon chain → higher boiling point

2. if same number of carbons, the more branching → lower boiling point

how to predict the direction a reaction will occur

if the reactant acid is stronger (lower pKa)→ favored direction is forwards

if the product conjugate acid is stronger (lower pKa)→ favored direction is reverse

bond angle for linear structure

180

bond angle for trigonal planar and bent geometry

120

bond angle for tetrahedral geometry

109.5

bond angle for trigonal bipyramidal geometry

90, 120, and 190

bond angle for octahedral geometry

90

acids

H donor

bases

H acceptor

amphoteric

can act as either base or acid depending on conditions

ex- H2O and R-OH

KA formula

[A-][H3O+]/[HA]

pKa formula

-log[Ka]

the smaller/more negative pKa is…

the stronger the acid

the larger KA is…

stronger acid

when adding a base to an acidic solution, what will the base always react with first

the most acidic H+ first

if the difference in pKa is ____, reaction essentially goes to completion (equilibrium)

pKa greater than or equal to 4

how does acidity change looking at the periodic table

going to the right on the periodic table, acidity increases

going down on the periodic table, acidity increases

atom bearing charge rule

the more acidic the atom, the better it stabilizes the negative charge

resonance rule for acids and bases

more resonance→ stronger acid/ weaker base

resonance spreads out and shares a negative charge among multiple atoms, which stabilizes the molecule

induction rule for acids and bases

the closer the more electronegative atom is to the H, the stronger the acid

orbital rule acids and bases

sp orbital is closer to the nucleus so it stabilizes the negative charge

strongest to weakest acids: sp>sp2>sp3

what is the strongest acid and its conjugate base

H2SO4

conj base: HSO4-

alkanes pKa value

>50 (very weak acid)

alkenes pKa value

44

amine pKa value

30-40

alkyne pKa value

25

anhydride group pKa

25

alcohol group pKa

16

alkyl halide pKa

50 (very weak acid)

acyl halide pKa

25

aldehyde pKa

17-18

carboxylic acid pKa

4-5

amide pKa

15-17

thiol pKa

10-11

sulfide pKa

40-45

ketone pKa

19-21

aromatic/arene pKa

43

ester pKa

25

ether pKa

45-50

which way does the reaction favor- the formation of the stronger acid or weaker acid

formation of weaker acid

How do you calculate the total number of electrons occupying sigma and pi bonding orbitals once you know the number of bonds

multiply by 2

how to determine how many nonbonding orbitals there are and how many electrons occupying them

look for lone pairs (1 pair= 1 nonbonding orbital)

multiply by 2 to get the number of electrons