LAB 1: Safety and Solubility

Question 1

What can highly polar, h bonding solvents like water dissolve?

Answer 1

polar compounds and salts

Question 2

Hexane is incapable of what?

Answer 2

H bonding, but it can dissolve large organic molecules (non-polar)

Question 3

What is insoluble in water?

Answer 3

compounds that contain carbon and hydrogen but no heteroatoms or heteroatoms that are built into the structure such that the dipole cancels, and compounds containing non - H bonding atoms (organic halides)

Question 4

Solubility is governed by?

Answer 4

Shape, size, nature of intermolecular forces. It also depends on how effectively the polar functional group can counteract the non-polar hydrocarbon character.

Question 5

What is distinctive of compounds with large carbon skeletons?

Answer 5

Compounds with more than 5 carbons are typically more able to dissolve in non polar substances even with a functional group that is polar

Question 6

What compounds contain polar functional groups?

Answer 6

alcohols, ketones, aldehydes, esters, amides

Question 7

Hydrogen bonding occurs…?

Answer 7

Hydrogen atom must be covalently bonded to electronegative atom such as O, N, F, etc and must interact with a nearby molecule that has an O or N (high EN atom) with a lone pair of electrons. It’s a strong dipole-dipole attraction.

Question 8

Homologous series

Answer 8

series of compounds with the same functional group and thus similar chemistry. The 5-carbon member is usually the upper limit to water solubility.

Question 9

How can you overcome the 5-carbon barrier?

Answer 9

The 5-carbon barrier can be overcome if the functional group can be changed into a charged species (salt formation-> deprotonation). Functional group (acidic or basic) is converted to its corresponding salt by acid base reaction.

Question 10

What is an acidic functional group?

Answer 10

R- OH or Ar- COOH

Question 11

What is a basic functional group?

Answer 11

R - NH2

R2 - NH

Question 12

Phenol

Answer 12

Benzene structure (6 carbons) with alcohol functional group. Largely non-polar.

Question 13

Salt formation test (NaOH)

Answer 13

• If organic compound is insoluble in water but dissolves in NaOH (aq) it probably contains more than 5 carbons and an acidic functional group
• Phenols can also be made more water soluble this way because phenoxide ion (Ar-O -) is resonance stabled

Question 14

Low pKa?

Answer 14

strong acid

Question 15

High pKa?

Answer 15

weak acid

Question 16

What can sodium bicarbonate (NaHCO3) be used for?

Answer 16

Used to distinguish between phenols and carboxylic acids. It is a strong enough base to deprotonate carboxylic acids. The reaction produces bubbles. Phenols are less acidic than carboxylic acids and do not react with NaHCO3 to form water-soluble salts. As a result, phenols are insoluble in 5% NaCHO3.

Question 17

Salt formation test (HCl)

Answer 17

Water insoluble organic compound that dissolves in aqueous acid probably contains more than 5 carbons and a basic functional group.

Question 18

In this experiment, a compound is soluble if…

Answer 18

if 0.01 g of the solute can dissolve in 1 ml of solvent at room temp

Question 19

Properties of NaOH

Answer 19

Caustic metal base. Dissolves readily in water. Can also dissolve in methanol and ethanol. Insoluble in ether and other non-polar substances.

Question 20

Properties of HCl

Answer 20

Polar bond due to electronegativity differences. Dissolves in polar substances like water readily.