Ketones.pptx

Ketones

1. Ketones

2. Introduction Ketones are organic compounds which incorporate a carbonyl functional group, C=O. The carbon atom of this group has two remaining bonds that may be occupied by hydrogen or alkyl substituents. If at least one of these substituents is hydrogen, the compound is an aldehyde. If neither is hydrogen, the compound is a ketone. The general formula for ketones is R 2 C=O where the R- group represents any alkyl. Examples: CH 3 - /Methyl CH 3 CH 2 -/ Ethyl CH 3 CH 2 CH 2 -/ Propyl CH 3 CH 2 CH 2 CH 2 -/ Butyl The ketones can be named systematically from the corresponding alkanes by changing the ending of each alkane to - yl followed by the word ketone after both alkyl groups are named, as in the form methyl ethyl ketone for CH 3 COCH 2 CH 3 . The common name for a ketone may be listed by molecular weight. Methyl is chosen first because it has a lower molecular weight than ethyl, with respect to the two alkyl groups on the C=O double bond If both of the alkyl groups are the same the numerical prefix di- is used, as in the case of dimethylketone . Dimethyl ketone is more commonly known by the trivial name acetone, and finds significant use as a solvent.

3. Introduction Dimethyl Ketone Methyl Ethyl Ketone For all except the simplest ketones, this form is not used and the ketone group is indicated systematically by use of the IUPAC system of nomenclature which assigns the suffix -one to ketones. Further, the parent chain includes the carbonyl group and is numbered so that the carbonyl location is the lowest number. The number of the location must be part of the name whenever there would be an uncertainty. Dimethyl ketone would be named 2-propanone, while methyl ethyl ketone would be named as a substituted butane, 2-butanone. However, in the case of both 2-propanone and 2-butanone the number is not necessary since these ketones cannot be arranged in any other order - There is no uncertainty. Notice: Propanone, Dimethyl Ketone and Acetone are Identical. A ketone carbonyl function may be located anywhere within a chain or ring, and its position is given by a locator number. Chain numbering normally starts from the end nearest the carbonyl group. In cyclic ketones the carbonyl group is assigned position #1, and this number is not cited in the name, unless more than one carbonyl group is present. When the suffix form cannot be used, perhaps because another suffix such as that of a carboxylic acid is required, the alternative designation -keto can be used for the ketone group. An example is 2-ketopropanoic acid.

4. Preparation Ketones can be prepared in a number of ways. the oxidation of secondary alcohols, the hydration of alkynes, the ozonolysis of alkenes, Friedel‐Crafts acylation, and the use of a Grignard reagent. Oxidation of secondary alcohols This way carried out using strong oxidizing agents . oxidizing agents include potassium dichromate (K 2 Cr 2 O 7 ) and chromic acid (H 2 CrO 4 ). Hydration of alkynes The addition of water to an alkyne leads to the formation of an unstable vinyl alcohol. These unstable materials undergo keto‐enol tautomerization to form ketones.

5. Preparation Ozonolysis of alkenes When one or both alkene carbons contain two alkyl groups, ozonolysis generates one or two ketones. The ozonolysis of 1,2‐dimethyl propene produces both 2‐propanone (a ketone) and ethanal (an aldehyde). Friedel-Crafts acylation It's used to prepare aromatic ketones. The preparation of acetophenone from benzene and acetyl chloride is a typical Friedel‐Crafts acylation.

6. Preparation Lithium dialkylcuprates The addition of a lithium dialkylcuprate (Gilman reagent) to an acyl chloride at low temperatures produces a ketone. This method produces a good yield of acetophenone. Grignard reagents Hydrolysis of the salt formed by reacting a Grignard reagent with a nitrile produces good ketone yields. For example , you can prepare acetone by reacting the Grignard reagent methyl magnesium bromide (CH 3 MgBr) with methyl nitrile.

7. Reactions Reduction of Ketones: Ketones can be reduced to alcohols using: Lithium aluminum hydride (LiAlH 4 ) Sodium borohydride (NaBH 4 ) Catalytic hydrogenation Nucleophilic addition of hydrogen cyanide: Cyanohydrin may be formed using liquid HCN with a catalytic amount of sodium cyanide or potassium cyanide.

8. Reactions Reaction with Grignard Reagent A Grignard reagent (a strong nucleophile resembling a carbanion, R: - attacks the electrophilic carbonyl carbon atom to give an alkoxide intermediate. Subsequent protonation gives an alcohol. Bisulfite addition The nucleophile is the hydrogen sulphite ion(HSO 3 ) This reaction is used for purification

9. Reactions Addition of alcohols (Acetal formation): Ketones react with two equivalents of alcohol to form acetals (sometimes called ketals in ketones). In an acetal, the carbonyl carbon from the ketone is singly bonded to two OR" (alkoxy) groups: Usually, acetals are used as a protecting group:

10. Reactions Addition of derivatives of ammonia: When ketones are treated with ammonia or its derivates (i.e. Y-NH 2 ) this (Y) could be hydrogen or alkyl group (imine), hydroxide group (oxime), or amine ( hydrazone ). When adding a 2 amine an (enamine) will be formed instead of (imine):

11. Reactions Ketones halogenation: Treatment of a ketone with halogen and either acid or base results in substitution of X for H on the ɑ carbon, forming an ɑ -halo ketone. Halogenation readily occurs with Cl 2 , Br 2 , and I 2 . Aldol reactions: It involves the combination of two carbonyl compounds to form a new β - hydrodxy carbonyl compound, this product is known as aldol ( ald ehyde + alcoh ol ). example:

12. Pharmacological effect When we look at the structures of our pharmaceuticals, we find that quite a few synthetic drugs do have ketones in their structures. Such as Moxifloxacin, Pranlukast ,Oxycodone Unoprostone ,Tolcapone, Rimexolone , Raloxifene and Nabumetone . Moxifloxacin : has a ketone segment just close to the carboxylic acid (COOH) group. it is an antibiotic used to kill bacteria. Unoprostone : This molecule is used to mimic a particular class of biochemicals, known as prostaglandins, which are made from fatty acids in our bodies.

13. Pharmacological effect Raloxifene : It has a ketone between two aromatic rings (flat rings), and is used to prevent particular types of breast cancer tumors from growing, because it interferes with steroids that interact with the tumors. Nabumetone : It is used to treat pain and swelling. It works much like aspirin, and contains a ketone as part of its structure.

14. Pharmacological effect Tolcapone It contains aromatic rings on both sides, we sometimes call this particular type of ketone a 'benzophenone’. This drug is used to treat neurological disorders associated with breakdown of biochemicals, helping to stop these chemicals from being degraded too fast. Oxycodone This is a modified alkaloid related to morphine, and is a pain-killer. It is best known as a part of OxyContin and responsible for hooking people on opiates.