OCHEM Fundamentals

wedge bonds

represent atoms coming out of the page

dashed bonds

represent atoms going into the page

constitutional/structural isomes

compounds with the same molecular formula but different connectivity of atoms

steric number

number of electron domains an atom has

steric number 4

sp3

1 s orbital = 25% s character

3 p orbitals = 75% p character

steric number 3

sp2

1 s orbital = 33% s character

2 p orbitals = 66% p character

steric number 2

sp

1 s orbital = 50% s character

1 p orbital = 50% p character

tetrahedral

sp3

4 bonds, 0 lone pairs

109.5°

ex: methane

trigonal pyramidal

sp3

3 bonds, 1 lone pair

<109.5°

ex: ammonia

bent

sp3

2 bonds, 2 lone pairs

<109.5

ex: water

trigonal planar

sp2

3 bonds, 0 lone pairs

120°

ex: ethylene, formaldehyde

bent

sp2

2 bonds, 1 lone pair

<120°

ex: pyridine

linear

sp

2 bonds, 0 lone pairs

180°

ex: acetylene

resonance rules

1. must maintain same skeleton (no movement of atoms)

2. be a valid Lewis structure

3. have same net charge

resonance hybrid

average of all of a molecule’s resonance structures and indicates areas of high and low electron density

most significant resonce contributor (more stable)

1. maximize the # of complete octets

2. minimize the # of formal charges

3. negative charge on more electronegative atom

   1. positive charge on less electronegratie atom

if an atom’s lone pair electrons are delocalized through resonance,

it does not contribute to the atom’s total # of electron domains

bronsted-lowry acid

proton donor

bronsted-lowry base

proton acceptor

bronsted-lowry acid-base reaction

a proton transfer occurs

products: conj base of acid and conj acid of base

lewis acid

electron pair acceptor

lewis base

electron pair donor

lewis acid-base reaction

lewis acid-base adduct is formed

nomenclature prefixes

1. meth-

2. eth-

3. prop-

4. but-

5. pent-

6. hex-

7. hept-

8. oct-

9. non-

10. dec-

carboxylic acid - prefix & suffix

n/a

-oic acid

ester - prefix & suffix

alkoxycarbonyl-

-oate

acid halide - prefix & suffix

halocarbonyl-

-oyl halide

amide - prefix & suffix

amido-

-amide

nitrile - prefix & suffix

cyano-

-nitrile

aldehyde - prefix & suffix

oxo-

-al

ketone - prefix & suffix

oxo-

-one

alcohol - prefix & suffix

hydroxy-

-ol

amine - prefix & suffix

amino-

-amine

alkene - prefix & suffix

alkenyl-

-ene

alkyne - prefix & suffix

alkynyl-

-yne

alkyl halide - prefix & suffix

halo-

n/a

ether - prefix & suffix

alkoxy-

n/a

nitro - prefix & suffix

nitro-

n/a

highest priority → lowest priority

1. carboxylic acid

2. acid anhydride

3. ester

4. acid halide

5. amide

6. nitrile

7. aldehyde

8. ketone

9. alcohol

10. amine

11. alkene

12. alkyne

13. akyl, halogen, alkoxy, nitro

strong acids

• low pK_a, high K_a

  • 7 strong acids include: Chloric acid (HClO3), Hydrobromic acid (HBr), Hydrochloric acid (HCl), Hydroiodic acid (HI), Nitric acid (HNO3), Perchloric acid (HClO4), and Sulfuric acid (H2SO4).

• acidity increases as we go down a column in ptable because atomic size increases

  • larger atoms are more acidic since their conjugate base is more stable (weaker)

strong bases

• high pK_a, low K_a

  • ex: NaOH, KOH, Ca(OH)₂, Ba(OH)₂

• acid base reactions favor formation of the weaker acid (higher pK_a)

What is the hybridization state and approximate bond angle of the nitrogen atom of N,N-dimethylformamide?

sp², 120°

What is the product of the following arrow-pushing mechanism? 

Identify the most acidic hydrogen in the compound below.

H₃ → If H3 is removed, the conjugate base is stabilized by resonance delocalization from the benzene ring. This resonance stabilization makes the conjugate base more stable, and hence, H3 is the most acidic hydrogen.