Occidental Petroleum Co., the nation's 12th-largest oil company, yesterday reported a 52.4 percent drop in its second-quarter profits and blamed the poor performance on the depressed world market for crude oil and chemicals.

Occidental earned $66.4 million (46 cents a share) in the second quarter, down from $139.6 million ($1.65) in the same period last year. Sales were up 38 percent to $4.3 billion vs. $3.1 billion.

Occidental's oil and gas earnings dropped to $87.1 million in the latest quarter from $160.2 million a year earlier.

Occidental's second-quarter coal earnings rebounded to $36 million from a loss of $32.6 million a year earlier and partially offset the lower petroleum and chemical results.

Boeing Co., blaming reduced deliveries of commercial jets and high costs, yesterday reported sharply lower earnings in the second quarter and first half.

Second quarter earnings were $71 million (74 cents a share), down 49 percent from $140 million ($1.46), in the same period last year.

Sales for the quarter were $2.39 billion, down 13.7 percent from $2.77 billion in the year-ago quarter.

For the six months, Boeing said earnings dropped 53.5 percent to $132 million ($1.37) from $284 million ($2.95) in the same period last year. Sales fell 15.2 percent to $4.48 billion from $5.19 billion.

Boeing Chairman T.A. Wilson said the decline in commercial earnings was partially offset by improved sales and earnings on U.S. government programs.

Greyhound Corp. yesterday reported second-quarter net income of $27.6 million (63 cents a share), down 12 percent from $31.4 million (70 cents) in 1981's second quarter.

Second-quarter revenue totaled $1.1 billion, down 8.3 percent from $1.2 billion in the same period last year, the company said.

First-half net income was $42.4 million (96 cents) on revenues of $2.2 billion compared with 64.3 million ($1.44) on revenues of $2.3 billion for the first half of 1981, the company said.

The 1981 first-half figures included a gain of $8.1 million from settlement of litigation with IBM and high gains in sales of equipment coming off lease.