Biochem_Lab_Exam

• 1,1-Dichloropropane
• 1,2-Dichloropropane
• 1,3-Dichloropropane
• 2,2-Dichloropropane

Butane



2-Methylpropane (isobutane)

• 1-Propanol
• 2-Propanol
• Ethyl methyl ether

Red is axial

Methane - Single Bond - 109.5 degrees

Ethylene - Double Bond - 120 degrees

Acetylene - Triple Bond - 180 degrees

• 
• Remember the "2" in 2-hexene means to place the double bond on the 2nd carbon.

The isomers are Stereoisomers (same connectivity but different orientation in space).

Toluene is not soluble in water because of the benzene ring. Toluene is soluble in methylene chloride because "Like Dissolves Like" and both toluene and methylene chloride are organic.

Remember: Most organics are insoluble in water but soluble in other organics and most burn or decompose quickly.

Unsaturated aliphatic hydrocarbons react rapidly with Br₂ and with KMnO₄ to produce distinct color changes. Saturated and aromatic hydrocarbons, on the other hand, require much more vigorous conditions. Thus, a compound that gives a positive test (clear) w/ Br₂ and/or KMnO₄ must be unsaturated, and a compound that gives a negative test (stays red) result must be saturated -or- aromatic.

• A positive reaction: C=C becomes 1,2-Dibromo-ethane and the solution turns from red (bromine) to clear
• 

KMnO₄ may be used as an oxidizing agent to differenciate between alkanes and alkenes.

The alkene's double bond changes to a single bond and OHs bond to the carbons that used to hold the double bond.



A cyclohexane would not react.

• Saturated hydrocarbons burn cleanly.
• Unsaturated and aromatic hydrocarbons burn with lots of soot

Toluene, an aromatic hydrocarbon, will give the most soot when ignited.

Ethylene a saturated hydrocarbon will give the least amount of soot.

Hydrocarbons are less dense than water.

0.816 g/mL x 5.00 mL = 4.08g

Note mL cancelled out.

• D = M/V therefore, M = D x V

The proof is two times the alcohol percentage... 190 proof

The technique of heating a liquid to its boiling point, condensing the vapors and collecting the condensate (distillate).

Works best with liquids that have a 100 degrees celsius or greater difference in boiling points.

"Repeated distillation" in the form of a fractionating column to increase the surface area within the distillation aparatus.

Fractional distillation works better than simple distillation for separating liquids that have boiling points which are less than 100 degrees celsius apart... even those that only within a few degrees of each other.

Steam distillation is a technique used for the vaporization of volatile, water-insoluble compounds with steam.

The steam for the distillation is generated from boiling water in the presence of the plant material. The theoretical basis of the technique is that a mixture of immiscible liquids will boil when their combined vapor pressures equal the opposing atmospheric pressure. Thus, the volatile organic compounds in a mixture will distill together with the water vapor and leave the nonvolatile compounds behind.

We obtain essential oils by boiling the plant material, collecting the steam with the essential oil within, and then isolating the oil by extracting it into an organic solvent such as ether, and then evaporating the solvent.

Two or more liquids form a constant boiling mixture of fixed composition.

The components of such a mixture can not be distilled.

• Boiling Point of Pentane = 36 degrees celsius
• Boiling Point of Heptane = 98 degrees celsius

No. Simple distillation works best when boiling points are 100 degrees celsius or more apart.

Possibly because they tend to have high molecular weights that outweigh the solubility of their polar parts and also because they contain aromatic rings that are not soluble in water.

R_f = spot divided by solvent

2.5 / 4.3 = 0.58

Non-polar moves faster.

Ordinarily, nonpolar compounds are more mobile than polar compounds.

Also, in general, the more polar a solvent is, the more effective it is at eluting (carrying) both polar and nonpolar compounds.

REQUIRES ANSWER

REQUIRES ANSWER

A chromophore is the part of a molecule responsible for its color.

A chemical group capable of selective light absorption resulting in the coloration of certain organic compounds.

The presence of certain unsaturated functional groups, called chromophores, nearly always results in color.

Common examples include retinal (used in the eye to detect light), various food colorings, fabric dyes (azo compounds), pH indicators, lycopene, β-carotene, and anthocyanins.

Common chromophoric groups include carbonyl (C=O), azo (N=N), nitro and aromatic polyenes.

Auxochromes intensify or augment color when present in a molecule with a chromophore, although they usually confer no color themselves.

Any radical or group of atoms that intensifies the color of a substance

Structurally, such groups possess non-bonded electron pairs, usually in the form of oxy or amino groups. As illustrations of these structural relationships, benzene and phenol are colorless, but nitrobenzene is pale yellow, and p-nitrophenol, which contains an auxochromic hydroxy group, is bright yellow.

Methyl orange is a pH indicator frequently used in titrations of acids...

More Acidic (below 3.1) is Red

More Basic (above 4.4) is Yellow

• In Lab pH 5.0 HCL solution Deep Red
• In Lab pH 11 NaOH solution Deep Orange

• 2-pentanol
• 

3-methylpentane



2-chlorobutane

• NEEDS ANSWER
• Enantiomers, the right- and left-handed forms of molecules, are defined as nonsuperimposable mirror images.

• Diasteromers are defined as stereoisomers that are not enantiomers. That is, if two molecular structures have all the same connections but they differe in the three-dimensional spatial orientations of their substituent group such that they are not mirror images of one another, then they are diastereomers.

In general, D-configuration refers to a Fischer projection in which the non-hydrogen group is on the right.

Note that D and L are means to describe the configurations of chiral centers. These are not to be confused with d and l, which describe the optical rotation properties of the compounds.

The clockwise (to the right) rotation of the plane of polarized light in a polarimeter.

The counterclockwise (to the left) rotation of the plane of polarized light in a polarimeter.

Showing that a compound rotates the plane of polarized light.

A mixture of equal amounts of two enantiomers.

Enantiomers are stereoisomers that are nonsuperposable mirror images; refers to a relationship between pairs of objects.

Epimers are diastereomers that differ in configuration of only one stereogenic center.

In chemistry, epimers are diastereomers that differ in configuration of only one stereogenic center. Diastereomers are a class of stereoisomers that are non-superposable, non-mirror images of one another.

The sugars α-glucose and β-glucose are epimers. In α-glucose, the -OH group on the first (anomeric) carbon is in the direction opposite the methylene group on carbon C-6 (in the axial position). In β-glucose, the -OH group is oriented in the same direction as the methylene group (in the equatorial position). These two molecules are both epimers and anomers.

The Molisch Reagent is used as a general test for any carbohydrate larger than a tetrose.

A positive result is indicated by a dark color (usually brown or purple).

The Benedict's Reagent is used as a general test for reducing sugars.

Formation of a voluminous red-orange dispersion is indicative of a reducing sugar.

The Barfoed's Reagent differentiates a reducing monosaccharide from a reducing disaccharide.

A positive test for reducing monosaccharide is indicated by the formation of a reddish precipitate within three minutes.

Barfoed's Test is a chemical test used for detecting the presence of monosaccharides. It is based on the reduction of copper(II) acetate to copper(I) oxide (Cu2O), which forms a brick-red precipitate.

• 

The Bial's Reagent differentiates a pentose from a hexose.

• A pentose is typically indicated by a greenish color.
• A hexose is indicated by a brownish color.

The Seliwanoff's Reagent differentiates aldohexoses and ketohexoses.

This test is based on the fact that, when heated, ketoses are more rapidly dehydrated than aldoses.

• The dehydrated ketose then reacts with the resorcinol to produce a deep cherry red color.
• Aldoses may react slightly to produce a faint pink color.

• The iodine reagent is used as a test for starch amylose.
• A positive result is indicated by a dark blue/black color.

• Starch amylopectin does not give the color, nor does
• cellulose, nor do disaccharides such as sucrose in sugar, nor glycogen.

Example of Saponification:

• 

Soaps form water-insoluble salts when used in water containing Ca(II), Mg(II), or Fe(III) ions (hard water).

2CH₃(CH₂)₁₄COO^-Na⁺ + Ca²⁺ --> [CH₃(CH₂)₁₄COO^-]₂Ca²⁺ + 2Na⁺

A sodium soap (soluble in water as micelles) plus Ca²⁺ results in a Calcium salt of a fatty acid (insoluble in water).

When soap and "dirt" are mixed together in water the nonpolar hydrocarbon inner parts of the soap micelles "dissolve" the nonpolar substances. In effect, new soap micelles form, with the nonpolar dirt molecules in the center. In this way, nonpolar organic grease, oil, and fat are "dissolved" and washed away in the polar wash water.

Soap owes its remarkable cleansing properties to its ability to act as an emulsifying agent.

Because the long hydrocarbon chains of natural soaps are insoluble in water, soap molecules tend to cluster in such a way as to minimize contact of their hydrocarbon chains with surrounding water molecules. The polar carboxylate groups, by contrast, tend to remain in contact with the surrounding water molecules. Thus, in water, soap molecules spontaneously cluster into micelles that surround 'dirt' and wash away in the rinse water.

• Bromine (Br₂) reacts with double bonds by turning them into single bonds. Unsaturated lipids have double bonds and saturated lipids do not. Thus bromine would not react with saturated lipids (staying reddish brown) but would react with unsaturated lipids (losing its color).

Synthetic detergents are a better emulsifying agent than soap because because detergent has a sulfonate (--SO₃^-) group instead of a carboxylate (--COO^-) group. Calcium, magnesium, and iron salts of alkylsulfonic acids (R-SO₃H) are much more soluble in water than comparable salts of fatty acids.

The Biuret test is a general test for any polypeptide larger than a dipeptide.

Formation of a violet (occasionally pink) color is a positive test.

The Ninhydrin Test is a general test for free amino acids.

Formation of a dark violet color is a positive test.

The Xanthoproteic Test is a diagnostic test for the presence of aromatic side-chains.

Formation of a dark orange-yellow color is a positive test.

Each may denature the protein molecule.

For example, heat cleaves hydrogen bonds, so boiling a protein solution destroys the alpha-helical and beta-pleated sheet strucure.

Acids may affect salt bridges thereby changing the formation/structure of the protein.

Alcohols may cause coagulation.

• Lead denatures proteins by attacking the --SH groups.

Any process that reduces enzymatic activity is known as inhibition.

Inhibition results when the active site is blocked by interaction with a molecule that is structurally related to the proper substrate.

Inhibition may be competitive or non-competitive and may result in partial or total loss of activity.

• a) Substrate concentration
• Saturation Curve. The rate does not increase continuously because a point is reached after which the rate stays the same even if we increase the substrate concentration further. At the saturation point, substrate molecules are bound to all available active sites of the enzymes.

• b) Enzyme Concentration
• The rate increases linearly because the molar concentration of enzyme is almost always much lower than that of substrate.

• c) Temperature
• Most enzymes have an optimal temperature of 37 degrees C. If we start below this temp and increase the temp the reaction rate will increase. However, if we get too hot we may alter the enzyme surface and the reaction rate will decrease.

• d) pH
• The curve is the same as with temps. There is an optimal pH (7.3 for humans). Too high or low decreases the reaction rate however within the narrow range of optinum increases...