Category: Organic Chemistry

• R-OH.
• Alcohols are molecules with the alkyl group attached to the —OH hydroxyl group.
• If a hydroxyl group is a substituent in a molecule, it’s called “hydroxy” or “—oxy” instead of “—oxyl”.
• A phenol is a benzene ring with an —OH attached. Phenols are abbreviated as Ar-OH. Ar is for aryl group. Phenols are weak acids and react with strong bases to make salt (alcohols do not salt out, only phenols).
• Due to the O (oxygen is very electronegative) and H, alcohols are polar and can create intermolecular hydrogen bonds.
• Alcohols can have the polar part and they can have the non-polar part. They can be soluble in a polar solvent like water.
• Due to both the London forces and H-bonds, alcohols have higher boiling and melting points.
• Alcohols have a pK(a) similar to water.
• Alcohols have the suffix -ol. In a ring, the OH group gets lowest-numbering (position) priority.
• If there is more than one OH group, use di-, tri-, etc.
• Some special alcohol structures are: 1,2-ethanediol (ethylene glycol); 1,2-propanediol (propylene glycol); 1,2,3-propanetriol (glycerol, glycerin).
• The carbinol carbon is the carbon that the OH group is attached to.
• An alcohol is: primary if the carbinol carbon is bonded to only one other carbon; is secondary if the carbinol carbon is bonded to two other carbons; is tertiary if the carbinol carbon is bonded to 3 other carbons.
• Alcohols can be made: hydration of an alkene; the reduction of an aldehyde or ketone.
• Reactions with alcohols: combustion; dehydration; condensation; oxidation; halogenation.

Methanol

• Wood alcohol.
• Toxic. Can cause blindness.
• Colorless & odorless.
• Fuel in race cars.

Ethanol

• The “alcohol” in beverages.
• Colorless & odorless.
• Product of carbohydrate fermentation.
• Used as solvent, antiseptic, fuel, treatment for alcohol poisoning.

2-Propanol

• Colorless & has a little odor.
• This is rubbing alcohol (typically sold in stores as diluted).
• Toxic to ingest.
• Disinfectant, astringent.

1,2-Ethanediol

• Sweet tasting but toxic.
• Antifreeze.

1,2,3-Propanetriol

• Glycerol.
• Viscous like honey.
• Sweet, non-toxic.
• Additive in foods and beverages.
• One of the products in fat-hydrolysis.
• Water soluble.
• Cosmetics, pharmaceuticals, lubricants, intermediates.

• Aromatics (or Benzene) are a special case of a cyclohexene. This cyclohexene alternates (all the way around) between double and single bonds. The structure has resonance so one configuration (e.g. single-double-single) can spontaneous switch/alternate (e.g. double-single-double) back and forth.
• When the benzene ring is a substituent, it is called a phenyl group (not to be confused with phenol, a benzene ring with a hydroxy substituent making it an alcohol).
• Aromatics do not easily undergo addition reactions, but rather substitution.
• Common reactions include: halogenation, nitration, and sulfonation.

• Alkynes have at least one triple bond in their structure.
• The general formula is C(n)H(2n-2).
• They are unsaturated.
• When naming, specify the positional number of the beginning of the double bond. Try to assign the lowest numbers to the multiple bond. Alkenes get priority over alkynes. If you have to prioritize, the double bond gets priority.
• If there is more than one double bond, use di-, tri-, etc.
• Alkynes end in -yne suffix.
• Naming: double and then triple bonds get priority over alkyl and halogen groups.
• Nonpolar. London forces are additive. When comparing, size comes first then packing efficiency.

• Alkenes have at least one double bond in their structure.
• The general formula is C(n)H(2n).
• They are unsaturated.
• When naming, specify the positional number of the beginning of the double bond. Try to assign the lowest numbers to the double bond. Alkenes get priority over alkynes.
• If there is more than one double bond, use di-, tri-, etc.
• Alkenes end in -ene suffix.
• Naming: double and then triple bonds get priority over alkyl and halogen groups.
• Alkenes and cycloalkanes can have cis- (same side) and trans- (opposite sides) descriptors. Cis- and trans- are specified at the beginning of the name.
• Alkenes may be cyclic.
• Nonpolar. London forces are additive. When comparing, size comes first then packing efficiency.
• The benzene ring (aromatic) is a special case of a cyclical alkene where the cyclohexene alternates between double and single bonds all the way around the ring. This special structure has resonance and the aromatics have a category all of their own.

• Consist of carbons and hydrogens only.
• n-alkanes have the general formula C(n)H(2n+1) where the parenthesis are subscripts.
• Can be straight chain (“n-“) or cyclic (“cyclo” prefix).
• Cycloalkanes have the general formula C(n)H(2n) where the parenthesis are subscripts.
• Find the longest chain. Branches off the longest chain are substituents. Number the chain such that the substituents have the lowest number. Substituents may be described by their position on the parent chain. E.g. 2,3-dimethylpentane. Use di-, tri-, etc. to describe how many substituents there are.
• Nonpolar. London forces are additive. When comparing, size comes first then packing efficiency.
• Consist of single bonds.
• Saturated.
• London forces which are also additive (e.g. the larger the molecule, the greater the london forces). The more “linear” the nature, the more surface area to “stack” the greater the intermolecular london force due to having more surface area to “stick”. In contrast, cycloalkanes have less sticking-surface area.
• Low melting/boiling points (increase with chain length/mass) .
• Usually less dense than water (increase with chain length/mass).
• C1 methane. C2 ethane. C3 propane. C4 butane. After that, the naming follows “normally” pent-, hex-, hept-, oct-, non-, dec-
• Carbons can be classifed as primary, secondary, tertiary, or quatenary depending on if it is bonded to 1 other carbon, 2 other carbons, 3 other carbons, or 4 other carbons respectively.

Cyclic Alkanes

• C(n)H(2n)
• Prefix “cyclo”
• Alkenes and cycloalkanes can have cis- (same side) and trans- (opposite sides) descriptors. Cis- and trans- are specified at the beginning of the name.

Alkyl Group

• Alkyl group is an alkane with one hydrogen removed.
• The alkyl group then acts as a substituent.
• CH3 methyl. CH3CH2- ethyl. CH3CH2CH2- propyl. CH3CH2CH2CH2- butyl. CH3CH2CH2CH2CH2- pentyl. Etc.

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It is easy to get confused between molecular vs. electronic geometry when studying VSEPR (valence shell electron pair repulsion). Molecular geometry is concerned with the arrangement of atoms; electronic geometry is concerned with the arrangement of electrons.

Using AXnEm notation, “Xn”; represents the number of atoms surrounding the central atom, A. “Em” represents the number of lone pairs.

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These are some tips to help you be more successful in collecting precipitate/crystals/powders etc.

1. Record the mass of clean, dry filter paper. Why? Because oftentimes it is difficult to separate out the filter paper from your product. If you know the mass of the clean, dry filter paper, then you can subtract its mass.
2. Record the mass of the “thing” you use to collect your product. That “thing” may be a watchglass, weigh-boat, crucible, beaker, dish, etc. You get the picture. IF you use a tape label, then make sure you weigh the mass of your watchglass (for example) WITH the label. Again, you can then subtract its mass later if needed. (E.g. if you screw up taring the balance).
3. PRE-WET the filter paper in the funnel with the solvent (usually chilled solvent). This keeps the edges of the paper down so it won’t shift and won’t “float” up when you dump the solution into the funnel.
4. Turn ON the vacuum BEFORE dumping a mixture into the funnel.
5. DISCONNECT tubing from your filtration system; disconnect from the vacuum BEFORE turning off the vacuum.

I just discovered this awesome free ochem book on lab techniques downloadable here (you don’t need a Dropbox account):

https://open.umn.edu/opentextbooks/textbooks/organic-chemistry-laboratory-techniques

Also, the website is probably a more updated version and is an excellent gen chem and ochem resource. I keep referring to their content in my studies:

https://chem.libretexts.org/Demos%2C_Techniques%2C_and_Experiments/Organic_Chemistry_Lab_Techniques_(Nichols)

And the general link here:

https://chem.libretexts.org/

They are such an awesome blessing to have!