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Physical properties of aldehydes and ketones
Boiling points, Solubility, REDOX and other reactions
29
Organic Chemistry
Undergraduate 1
02/19/2015

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Term
Tollen's Test
Definition
Distinguishes between aldehydes and ketones.  Ag+ and ammonia oxidizes aldehydes but not ketones.  A "silver mirror" is formed if the silver ion is reduced by an aldehyde.
Term
Benedict's Test
Definition

Gives a positive result with an aldehyde functional group with an adjacent hydroxyl group.  Cu^2+ added to aldehydes and reheated.  A brick-red color and solids show positive.  It is negative with simple aldehydes and ketones.

Positive:

CH3-CH-C-H

                           |   ||                      

             OH  O         

Term
What are needed to reduce aldehydes and ketones?
Definition
Sodium Borohydride (NaBH4) and Hydrogen (H2).  A nickel, platnum or palladium catalyst is used.
Term
What forms when you reduce an aldehyde?
Definition

Primary Alcohol

CH3-CH2-C-H + H2 -> CH3-CH2-CH2-OH

               ||                                            

  O                               

Term
What forms when you reduce a ketone?
Definition

Secondary Alcohol

CH3-C-CH3 +H2 (Ni) -> CH3-CH-CH3-OH

    ||                                                

 O                                             

Term
What is one of the most common reactions of aldehydes and ketones?
Definition
Addition of polar molecules to the carbonyl group which is reactive due to the polarity of the C=O double bond.
Term
What occurs in addition reactions?
Definition

The partially negative part of the adding molecule bonds with the partially positively charged carbonyl carbon.

                                 

                                O-X

      \                     \  /      

C=O + X-Y ->  C

/                     / \

                            Y

Term
Name the relative boiling points and forces for the current molecules.
Definition

Alkane -> Ether -> Aldehyde -> Ketone -> Alcohol

Dispersion-> Weak dipole  -> Middle dipole -> Strong dipole -> Hydrogen

Term
What are physical properties of Aldehydes (partly due to the carbonyl group)
Definition

Higher boiling points than alkanes and ethers of similar mass due to the Dipole bonding

Lower boiling points that alcohols of similar mass

Term
Carbonyl compounds wth 1-4 carbons have what kind of water solubility?
Definition
Very high to high
Term
Carbonyl compounds with 5 carbons have what kind of solubility?
Definition
Weak
Term
Carbonyl compounds with 6 or more carbons have what knd of water solubility?
Definition
None
Term
When you add water to aldehydes and ketones, what do you create?
Definition
Carbonyl Hydrates
Term
How does the addition of water work with the carbonyl group?
Definition
The partially negative -OH group bonds with the carbon.  The -H bonds with the partially negative oxygen.
Term
What is the name of formaldehyde when it goes through a water addition reaction and forms a hydrate?
Definition
Formalin
Term
What is the name aldehydes other than Formaldehyde get when they go through an addition of water reaction?
Definition
Hydrate
Term
Describe the formula for the reaction of formaldehyde with water
Definition
CH2=O + H2O -> OH-CH2-OH
Term
Describe the formula for acetaldehyde with it goes through a water addition reaction
Definition

                       H

                       |

CH3-CH=O -> CH3-C-OH

                        |

                          OH

Term
What is the name of an aldehyde with chlorine atomes?
Definition
Chloral
Term
When a chloral goes through a water addition reaction, describe what is formed.
Definition

                         OH

                       |

Cl3C-C=O -> Cl3C-C-OH

               |                   |            

        H                   H     

Term
What forms when aldehydes and ketones react with alcohols in the presence of an acid catalyst?
Definition
Acetals
Term
What is the acetal product after an aldehyd or ketone reacts with alcohol.
Definition
2 alkoxy groups are added to the carbonyl carbon and water is released.
Term
What is the product of acetaldehyde + 2 methyl alcohol? (Acetal formation)
Definition

Acetaldehyde dimethyl acetal

        O-CH3      

                  |                        

CH3-C-H + H2O

|       

         O-CH3       

Term
What is the product of Propanone + 2 Ethyl alcohol? (Acetal formation)
Definition

Propanone diethyl acetal

 

            O-CH2-CH3      

                  |                           

CH3-C-CH3 + H2O

|          

        O-CH2-CH3  

Term
What is an alkoxy group?
Definition
-O-CH3 as a substituent group
Term
What is the name of the intermediary step when combining an aldehyde with alcohol?
Definition

Hemiacetal

Halfway to an acetal

(Hemi- part way, -acetal to an acetal.)

Term
What is going on during the hemiacetal stage of combining an aldehyde to an alcohol?
Definition

The first of the 2 alcohol molecules bnds to the carbonyl carbon, forming a hydroxyl group on the O and an alkoxy group to the same carbon atom.

Acetaldehyde+Methyl alcohol->Hemiacetal Intermediate

                                                 O-CH3

                                         |

CH3-CH=O + CH3-OH -> CH3-C-H

                                         |

                                           OH

Term
How is a cyclic hemiacetal formed?
Definition

When the carbonyl group and the -OH group are on the same molecule

HO-C-C-C-C-C-H

                ||

                O

A cyclic hemiacetal is formed with 1 Oxygen in the formed molecule and an H and -OH group off of the following carbon.

Term
Are 5 and 6 atom cyclic hemiacetals and acetals more or less stable than their open-chained structures?
Definition
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